Scientific Calendar

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Each year, ICTP organizes more than 60 international conferences, workshops, and numerous seminars and colloquia.

Interested in attending an activity? Complete an online application form: Events in the calendar that have an "smr" number require an application. Click on the activity and complete the online application form.

External organizations can pay for and organize their own high-level scientific and cultural events at ICTP. Details for these "Hosted Activities" are available in the Logistic Guidelines for Hosted Activities (pdf download).

Europe/RomeWe study the number of clusters in 2d critical percolation, NΓ , which intersect a given subset of bonds, Γ. In the simplest case, when Γ is a simple closed curve, NΓ is related to the entanglement entropy of the critical diluted quantum Ising model, in which Γ represents the boundary between the subsystem and the environment. Due to corners in Γ there are universal logarithmic corrections to NΓ , which are calculated in the continuum limit through conformal invariance making use of the Cardy-Peschel formula. The exact formulae are confirmed by large scale Monte Carlo simulations. These results are extended to anisotropic percolation where they confirm a result of discrete holomorphicity.
I. A. Kovács, F. Iglói and J. Cardy, Phys. Rev. B 86, 214203 (2012), arXiv:1210.4671
ICTPICTPpio@ictp.it

Europe/RomeAbstract: The next few years will bring a wealth of new information about the primordial cosmological fluctuations. In this talk, I will discuss how observable non-Gaussianities and gravitational wave signals encode the physics of the early universe. First I will discuss signatures of global symmetries in the early universe, arguing that even the simplest slow roll inflation models can lead to observable non-Gaussianity and primordial gravity waves. Next, I will consider more generally the possibility to probe how the inflaton couples to radiation.ICTPICTPpio@ictp.it

Europe/RomeA single vacancy in an otherwise clean flake of graphene introduces a topological defect. It punches a new state at zero energy into the Dirac cone (zero mode). A finite concentration of such vacancies produces a narrow impurity band that determines the low energy/frequency response of the flake. A peculiarity of this band is that its properties are very sensitive to details of the impurity placings:
All impurities in one sublattice imply a density of states (DoS) vanishing in the zero energy limit, while impurities distributed equally over both sublattices (compensated) exhibit a diverging DoS.
We present a numerical study focussing mainly on the DoS at very low energies. We resolve the Dyson-singularity with compensated disorder and investigate the amplitude statistics (multifractality) of the associated wavefunctions. Finally, we present transport calculations addressing the possibility of Anderson-localization on percolation clusters preempting the classical localization transition.
ICTPICTPpio@ictp.it

Europe/RomeAbstract: F-theory marks a major step forward in understanding the strong coupling regime of type IIB string theory. However, it has a perturbative formulation in terms of the string length, being on the same footing as type IIB supergravity. Controlling \alpha' corrections to the F-theory effective physics is a challenging task and is of great relevance in string phenomenology. In this talk, I will present a modest attempt in this program. In particular, I will be mostly focusing on F-theory compactified on K3xK3 and discuss the exact Kaehler potential in the \alpha' perturbation theory for the vector multiplets of the ensuing 4d, N=2 effective theory. The various (non)-perturbative dualities which this specific model features greatly simplify the analysis and makes manifest the SL(2,Z)-invariant structure of the quantum corrections. I will finally interpret these corrections in 11d supergravity and provide a way of computing them directly in the M-theory definition of F-theory.
ICTPICTPpio@ictp.it

Europe/RomeI will survey some recent ideas and results on transport and dynamics of excited interacting systems with and without disorder. While in some cases existence of macroscopic diffusion can be verified, in other cases, e.g. in the presence of localization on microscopic scales, emergence of diffusion may be thwarted. The conditions for existence of such many body localized phases appear to be generic, provided the disorder is strong and interactions are sufficiently short ranged.SISSA, Santorio Building, Room 128 (1st Floor)ICTPpio@ictp.it

Europe/RomeI will introduce Tensor Network states and explain in this context two strategies for extracting universal quantities at conformal invariant fixed point of spin chains. One of them the scaling approach is better suited to simple tensor networks such as matrix product states and tree tensor networks. More sophisticated tensor networks (such as the MERA) allow to directly extract universal properties from the tensors of the network.
I will present results obtained through both approaches.ICTPICTPpio@ictp.it

Cosponsor(s):
the International Commission for Optics (ICO), the Optical Society of America (OSA), the International Society for Optics and Photonics (SPIE), the European Optical Society (EOS), the Società Italiana di Ottica e Fotonica (SIOF), the US National Academy of Sciences (NAS), the Photonics Society (IEEE), and the International Society on Optics Within Life Sciences (OWLS)

Europe/RomeThe entanglement spectrum, ie the logarithm of the eigenvalues of reduced density matrices of quantum many body wave functions, has been the focus of a rapidly expanding research endeavor recently. Initially introduced by Li & Haldane in the context of the fractional quantum Hall effect, its usefulness has been shown to extend to many more fields, such as topological insulators, fractional Chern insulators,
spin liquids, continuous symmetry breaking states, etc.
After a general introduction to the field we review some of our own contributions to the field, in particular the perturbative structure of the entanglement spectrum in gapped phases, the entanglement spectrum across the Mott-insulator transition in the Bose-Hubbard model, and the relation of the entanglement spectrum of (1+1) dimensional quantum critical systems to the operator content of their underlying CFT.
ICTPICTPpio@ictp.it

Europe/RomeWe consider a spin-orbit (SO) coupled configuration of spin-1/2 interacting bosons with equal Rashba and Dresselhaus couplings. The phase diagram of the system at T=0 is discussed with special emphasis on the role of the interaction, treated in the mean-field approximation. For a critical value of the density and of the Raman coupling we predict the occurrence of a characteristic tricritical point separating the stripe, the spin polarized and the zero momentum states of the Bose gas. The role of the breaking of spin symmetry in the interaction Hamiltonian, as well as the compressibility and the spin polarizability of the system are discussed.
By using the hydrodynamic formalism we identify the excitation spectrum at zero temperature. The propagation of phonons is strongly affected by the SO coupling and the velocity of sound vanishes when one approaches the second order phase transition between the spin polarized and the zero momentum quantum phases. We also point out the emergence of a roton minimum in the excitation spectrum for small values of the Raman coupling, when one approaches the transition to the stripe phase.
ICTPICTPpio@ictp.it

Europe/RomeIn this talk I will present some complex, NP-complete problems, formulated in Clifford (spinor) Algebra. I will show that typically these problems require only a polynomial number of Clifford multiplications. I will then treat briefly the computational complexity of Clifford operations.
Subsequently I will present some results for Clifford algebras in arbitrary dimension that allow to better tackle the initial formulation of the complex problems.
SISSA, Santorio Building, Room 128 (1st Floor)ICTPpio@ictp.it

Europe/RomeAbstract:
We present some spectral conditions in order to describe the phase portrait of a planar vector field, in a neighborhood of infinity. Suppose that X is a planar vector field whose linearization outside some compact set is Hurwitz: it admits to the origin as a linear hyperbolic attractor. Then by adding to X a constant vector, one obtains that the infinity is either an attractor or a repellor.
ICTPICTPpio@ictp.it

Europe/RomeWe investigate, using series expansion techniques, the effects of higher-body local interactions in softcore lattice bosons and find that there is a systematic procedure to exactly renormalize the two-body interactions at every perturbative order; this is found to be applicable to quantum critical as well as ground state properties within the Mott insulating lobe. Preliminary work on finite temperature effects in interacting hardcore bosons (XXZ-type spin models) will be briefly mentioned.ICTPICTPpio@ictp.it

Europe/RomeAbstract:In the early 80’s, V. Mehta and A. Ramanathan proved two restriction theorems which proved to be of central importance to the study of vector bundles in the subsequent years. The theorems roughly state that if X is a smooth projective variety over a field k = k with a polarisation H and V is a vector bundle on it which is semistable (resp. stable) w.r.t. H, then the restriction of V to a general, complete intersection curve of sufficiently high degree is again semistable (resp stable).
I will explain these theorems in detail and sketch a proof in some special cases. If time permits some applications will also be discussed.ICTPICTPpio@ictp.it

Seminar

14 Feb 2013

@ ICTP

Mathematics

Europe/RomeWith V. Golyshev.
This talk is an example of how some cases of Langlands' correspondence for function fields can be interpreted very classically and explicitly. Whenever we have an explicit description of Hecke operators in the Langlands setup, we obtain some elementary identities between special functions. In particular, we see how formulas of Clausen's type and multiplication identities for Bessel functions arise this way.
As an application to arithmetic, our method gives a direct correspondence between solutions of the Dwork's accessory parameter problem as studied by Beukers, and automorphic forms over P^1 with four marked points as described by Kontsevich.ICTPICTPpio@ictp.it

Europe/RomeThe integration of various types of genomic data into predictive models of biological networks is one of the main challenges currently faced by computational biology. Constraint-based models in particular play a key role in the attempt to obtain a quantitative understanding of cellular metabolism at genome scale. In essence, their goal is to frame the metabolic capabilities of an organism based on minimal assumptions that describe the steady states of the underlying reaction network via suitable stoichiometric constraints, specifically mass balance and energy balance (i.e. thermodynamic feasibility). The implementation of these requirements to generate viable configurations of reaction fluxes and/or to test given flux profiles for thermodynamic feasibility can however prove to be computationally intensive. We propose here a fast and scalable stoichiometry-based method to explore the Gibbs energy landscape of a biochemical network at steady state. The method is applied to the problem of reconstructing the Gibbs energy landscape underlying metabolic activity in the human red blood cell, and to that of identifying and removing thermodynamically infeasible reaction cycles in the Escherichia coli metabolic network (iAF1260). In the former case, we produce consistent predictions for chemical potentials (or log-concentrations) of intracellular metabolites; in the latter, we identify a restricted set of loops (23 in total) in the periplasmic and cytoplasmic core as the origin of thermodynamic infeasibility in a large sample of flux configurations generated randomly and compatibly with the prior information available on reaction reversibility.ICTPICTPpio@ictp.it

Europe/RomeAbstract. Very light axion-like particles (ALPs) with a two-photon vertex are predicted in many extensions of the Standard Model of particle physics. Depending on the actual value of their mass, ALPs can play an important role in cosmology, either as cold dark matter particles or as quintessential dark energy. The coupling with photons allows for ALP-photon mixing in external electromagnetic fields. This effect is exploited for direct searches of ALPs in laboratory experiments. The two-photon vertex would also induce the mixing with ALPs for photons emitted by distant astrophysical sources, and propagating in the large-scale cosmic magnetic fields. Indeed, different astrophysical puzzles would be naturally solved by conversions of cosmic photons into ALPs. Motivated by these intriguing hints, I will discuss how current and upcoming astrophysical experiments, ranging from the cosmic microwave background to the high-energy gamma-rays, could probe the elusive ALPs in a region of their parameter space not accessible by laboratory experiments. ICTPICTPpio@ictp.it

Europe/RomeHigh-temperature superconductivity in the copper oxides is almost universally associated with strong electron-electron correlations, and the idea that superconductivity appear doping a Mott insulator. The iron-based superconductors do not seem to follow the same paradigm, as the parent compounds are not insulating despite their magnetic ordering. Another key difference is that, while the cuprates can be described with a single valence band, in the iron materials it appears necessary to consider all five iron d-orbitals.
Re-examining the experimental data for the effective mass, we show that indeed the phase diagram of iron superconductors is controlled by a Mott insulating state which would occur in a material with a very large hole-doping, while the parent compound is not close to a Mott state despite the commensurate filling.
The reason for this behavior is a large Hund's coupling, which decouples the orbitals turning the multi orbital bandstructure into a collection of single-band Hubbard models. This finding creates the strongest connection between cuprates and iron superconductors. In both cases superconductivity appears around 20% doping of a Mott insulator.
As a matter of fact the different single-band models have a different population (or doping) and therefore they have a different effective mass, which simply corresponds to the distance from the Mott insulator. This also implies a strongly "orbital-selective" effective mass, which reconciles contrasting evidences of correlations in these materials.
ICTPICTPpio@ictp.it

Europe/RomeThe space of Kahler-Einstein (KE) Fano manifolds can be naturally compactified by considering metric degenerations in the so-called Gromov-Hausdorff topology. The relation between the existence of a KE metric and an algebro-geometric notion of stability of the underlying variety (Yau-Tian-Donaldson Conjecture, now a theorem), suggests that the above metric compactification should correspond to certain compact algebraic moduli spaces of stable Fano varieties (K-Moduli).
In this talk we will describe the general picture, focusing on the understood case of Del Pezzo surfaces (joint work with Yuji Odaka and Song Sun).ICTPICTPpio@ictp.it

Europe/RomeI will discuss finite volume matrix elements of local operators in integrable quantum field theories and present a conjecture relating finite and infinite volume form factors in the most general setting, i.e. including the case of form factors containing disconnected pieces in the presence of non-diagonal scattering. Specializing to the sine-Gordon model, finite volume multi-soliton form factors are compared to numerical data coming from a numerical renormalization group calculation in the truncated conformal space. I find excellent agreement between the two approaches, thus verifying both bootstrap for multi-soliton form factors and the theory linking finite and infinite volume matrix elements. Evaluation of the nontrivial multi-soliton form factors is achieved by a newly developed regularization scheme.
SISSA, Santorio Building, Room 128 (1st Floor)ICTPpio@ictp.it

Europe/RomeWe develop the theoretical study of a novel physical system, in the context of ultracold gases. We investigate the physical behavior of a resonant Bose-Fermi mixture, namely, an ultracold gas made of both bosons and fermions, with a strong attractive interaction between these two components.
We study homogeneous density and mass imbalanced mixtures from weak- to strong- coupling limit, comparing the results obtained with two different theoretical approaches, a many-body diagrammatic approach (the T- matrix approximation) and Quantum Monte Carlo method.
By using many-body diagrammatic methods we first obtain the finite-temperature phase diagram and the thermodynamic properties of the system. We observe the presence of a quantum phase transition from the condensed (superfluid) to the normal (molecular) phase. Developing the zero-temperature limit of the same Green’s function formalism we study the effect of density and mass imbalances for the Bose-Fermi mixture. By using the corresponding retarded propagators we calculate the spectral weight functions and the dispersions of bosons and fermions.
We apply for the first time the Quantum Monte Carlo method with Fixed-Node approximation to investigate resonant Bose-Fermi mixture, from weak to strong boson-fermion attraction. Two different nodal surfaces are used as trial wave functions in the two regimes. We obtain the equation of state of a density imbalanced mixture and we observe the presence of the quantum phase transition through the crossing of the energies, calculated with their respective trial wave functions. A phase diagram in the coupling and boson-fermion concentration variables is derived and the occurrence of phase separation is discussed. We compare Quantum Monte Carlo results to T-matrix calculations, finding an interesting agreement between the results.
ICTPICTPpio@ictp.it

Europe/RomeThe structures of metallic nanoparticles are searched for by a computational methodology combining global optimization searches within an atomistic model and density-functional local relaxation. Different systems are considered, from single-metal nanoparticles adsorbed on magnesium oxide, to free and supported nanoalloys.
Metallic nanoparticles adsorbed on MgO are of great interest for applications in catalysis. Here we show that a variety of different morphologies can be obtained depending on the magnitude of the lattice mismatch and on the interaction strength with the substrate. We consider Au, Ag and Ni clusters on MgO(100) and compare our results with the experimental findings.
Nanoalloys with core-shell arrangement are of special interest in applications, such as in optics, catalysis, magnetism and biomedicine. Despite this wide interest, the physical factors stabilizing the structures of these nanoparticles are still unclear to a great extent, especially for what concerns the relationship between geometric structure and chemical ordering.
Here global-optimization searches are performed in order to determine the most stable chemical ordering patterns corresponding to the most important geometric structures, for a series of weakly miscible systems, including AgCu, AgNi, AgCo andC AuCo. Our calculations show that
a) the overall geometric structure of the nanoalloy and the shape and placement of its inner core are strictly correlated; b) centered cores can be obtained in icosahedral nanoparticles but not in crystalline or decahedral ones, in which asymmetric quasi-Janus morphologies form;
c) in icosahedral nanoparticles, when the core exceeds a critical size, a new type of morphological instability develops, making the core asymmetric and extending it towards the nanoparticle; d) multi-center patterns can be obtained in large polyicosahedral nanoalloys.
Analogies and differences between the instability of the core in icosahedral nanoalloys and the Stranski-Krastanov instability occurring in thin-film growth are discussed. All these issues are crucial for designing strategies to achieve effective coatings of the cores.
SISSA, Santorio Building, Room 131 (1st floor)ICTPpio@ictp.it

Europe/Rome2D physical systems with degenerate grounds states and excited particle states obeying exotic statistics ('anyons') provide a surprisingly effective and aesthetically appealing arena for performing quantum
computation. Topological quantum computation is a rapidly expanding research area focused on the physical realisation of a quantum computer that is intrinsically fault-tolerant and decoherence free. The theoretical background needed for dealing with 'topological' systems and materials will be presented in an pedagogical way.
ICTPICTPpio@ictp.it

Europe/RomeAbstract: We solve the semiclassical Einstein equations governing the dynamics of linear metric perturbations (of scalar, vector and tensor type) around de Sitter spacetime including the vacuum polarization effects of conformal matter fields. An order reduction method is used to eliminate the spurious solutions associated with higher order derivatives. Our exact (nonperturbative) solutions show that de Sitter spacetime is stable and a large time attractor. This extends some of the existing â€œno-hairâ€ results for de Sitter spacetime. ICTPICTPpio@ictp.it

Europe/RomeThe statistics of work done and associated fluctuation theorems give a novel thermodynamic interpretation of dynamics in quantum systems. Here, we apply the fluctuation theorems to a sudden "quench" of a quantum system of many interacting particles containing a critical point. The results highlight that the fluctuations of a dynamical quantum system provide a route understanding the emergence of thermodynamic irreversibility. Furthermore I will show that the characteristic function of the work distribution for a non-equilibrium process can be extracted from Ramsey interferometry of a single probe qubit. Our scheme paves the way for the full characterisation of non-equilibrium processes in a variety of complex quantum systems, ranging from atomic systems to NMR.ICTPICTPpio@ictp.it

Europe/RomeLithium ion transport attracts much interest because it is fundamental process at lithium ion battery electrodes, particularly at nanowire electrodes. To study irreversible transport process at charging–discharging process directly at atomic scale, we developed an aberration corrected electron microscope which allows us to form an electron probe having a diameter of sub-50pm. The spherical electron wave emitting from the electron probe scans the specimen surface was found for the first time to give structure image of individual lithium ions. In electrodes of spinel structure, i.e., LiMn2O4, dislocation of lithium ions from the tetrahedral sites induces local structure change at octahedral sites, which makes charging-discharging cycle of ion transport irreversible#). Structure change is discussed in relation to the current-voltage relation of a mode LIB. At excess or deficient concentration of lithium ions, spinel electrodes exhibited local disorder. To characterize local disorder, we devised a new method which can allow us to find not only pair correlation but also higher order correlation of the local disorder.
#)This work is supported by CREST project, “nanocycle at nano-in-macro interface”
ICTPICTPpio@ictp.it

Europe/RomeMAIN TOPIC: Conformal Field Theories in Higher Dimensions and the Conformal Bootstrap
The Aim of the School is to bring together theoretical physicists of all levels who want to learn both Mathematica and a selected advanced research topic on Theoretical Physics. The courses on Mathematica will be given focusing on examples borrowed from the topic related to conformal symmetry in field theory. Previous editions of the School took place in Porto (2009 and 2010), Waterloo (2011) and São Paulo (2012). See http://msstp.org/ for more information about the previous schools.
LECTURERS INCLUDE:
R. CAVALIERE (Adalta - Divisione Wolfram Research, Italy)
D. GAIOTTO (Perimeter Institute, Canada)
G. KORCHEMSKY (CEA Saclay, France)
J. PENEDONES (Porto University, Portugal)
D. SIMMONS-DUFFIN (SNS-IAS, USA)
P. VIEIRA (Perimeter Institute, Canada)Trieste - ItalyICTPpio@ictp.it

Activity

Europe/RomeThe equilibrium and nonequilibrium quantum evolution of extended observables and entanglement properties are discussed in systems of Fermi gases/liquids of any dimension. In particular I focus on the entanglement entropy of extended space regions at equilibrium and off-equilibrium during the expansion after the drop of a trapping potential, which generally shows multiplicative logarithmic corrections to the leading power-law behaviors, analogously to the logarithmic corrections to the area law in lattice fermions.SISSA, Santorio Building, Room 128 (1st Floor)ICTPpio@ictp.it

Europe/RomeThe study of an almost Ricci soliton was introduced in a recent paper due to Pigola, Rigoli, Rimoldi and Setti. This structure represents a generalization to Einstein metrics and Ricci soliton, they appear as special solutions of the Ricci flow. In this seminar we shall talk about two results. The first treats of the characterization of compact almost Ricci solitons , more precisely, in this work we find some structure equations for almost Ricci solitons which generalize the equivalent for Ricci solitons. As a consequence of these equations we derive an integral formula for the compact case which enables to show that a compact nontrivial almost Ricci soliton is isometric to a sphere, provided either it has constant scalar curvature or its associated vector eld is conformal. Next, we prove that any compact almost Ricci soliton with constant scalar curvature is isometric to a Euclidean sphere. As a consequence we obtain that every compact almost Ricci soliton with constant scalar curvature is gradient.ICTPICTPpio@ictp.it

Europe/RomeQuantum many-body physics has traditionally been dominated by detailed investigations of equilibrium properties and low-energy excitations. In the last decade or so, motivated by novel experimental possibilities such as cold atoms, the study of quantum matter far from equilibrium has emerged as an important and exciting new field.
I will start with a selection of new questions and phenomena that have appeared in the context of non-equilibrium evolution in isolated systems. I will end by focusing on a specific example, namely, the dynamics of composite objects in lattice systems. such as repulsively bound pairs, triplets and clusters.
ICTPICTPpio@ictp.it

Europe/RomeAbstract: We explore the dynamics of metric perturbations (gravitational waves) on the cosmological background in the theory with higher derivatives and semiclassical non-local corrections coming from massless conformal fields. It is shown, by means of analytical and numerical methods that there are no growing modes until the background has enegies of Planck order of magnitude. This result means, also, that there are good chances to construct renormalizable theory of quantum gravity which is unitary for the energies below Planck scale.ICTPICTPpio@ictp.it

Europe/RomeFor sensory networks, we determine the rate with which they acquire information about the changing external conditions. Comparing this rate with the thermodynamic entropy production that quantifies the cost of maintaining the network, we find that there is no universal bound restricting the rate of obtaining information to be less than this thermodynamic cost. These results are obtained within a general bipartite model consisting of a stochastically changing environment that affects the instantaneous transition rates within the system. Moreover, they are illustrated
with a simple four-states model motivated by cellular sensing. On the technical level, we obtain an upper bound on the rate of mutual information analytically and calculate this rate with a numerical method that estimates the entropy of a time-series generated with a simulation.
ICTPICTPpio@ictp.it

Europe/RomeAbstract: There are three types - three "flavors" of neutrinos: electron, muon and tau. Enormous progress in neutrino physics was related to the discoveries of flavor oscillations and flavor conversion of neutrinos in matter. These discoveries allowed us to detrmine the neutrino mass parameters and mixing and to elaborate neutrino "flavor optics". I will describe recent developments in the field which include measurements of the 1-3 mixing, searches for new (flavorless) neutrinos, attempts to understand the origins of neutrino mass. I will outline possible future progress in the field.ICTPICTPpio@ictp.it

Activity

Europe/RomeRecent experimental progress in the physics of ultracold atomic gases has revived the interest in the behavior of thermally isolated quantum statistical systems, especially after sudden changes (quenches) of their control parameters. Considering the quench as a thermodynamic transformation, it is natural to focus on the irreversible work done on the system, which is characterized by a certain probability distribution. By studying its large deviations, i.e., rare fluctuations of the work per unit volume, we establish a connection with the physics of a classical system confined in a film geometry. If the system is quenched close to a (quantum) critical point, both the edge singularity and the large deviations of the irreversible work acquire universal features dictated by the critical Casimir effect in the corresponding classical system. In systems of bosons, the statistics of the work may additionally display a transition which is analogous to the equilibrium Bose-Einstein condensation.ICTPICTPpio@ictp.it

Europe/RomeAbstract: Gauge theories, such as the one describing strong interactions, contain string-like excitations. String theory describes the quantum dynamics of strings and it reduces to gravity at long distances. The simplest versions of string theory live in a ten dimensional spacetime. We will explain how these ten dimensional strings are intimately connected to the strings that appear in four dimensional gauge theories. The four dimensional gauge theory gives rise to a gravitational theory in a higher dimensional curved spacetime. The gravitational theory is simple to analyze when the four dimensional theory is strongly interacting. This provides a simple way of studying strongly coupled phenomena en quantum field theories. In addition, it can be used to describe black holes in a fully quantum mechanical fashion. ICTPICTPpio@ictp.it

Europe/RomeAbstract: Several unexplained results from neutrino oscillation experiments and from cosmology have sparked renewed interest in extensions of the Standard Model containing light sterile neutrinos. In this talk, we first discuss the status of such models, we present results from a global fit to neutrino oscillation data, and we discuss the tension between different data sets. In the second part of the talk, we explore the possible implications that the existence of sterile neutrinos could have for dark matter searches. In particular, resonantly enhanced active-to-sterile oscillations can weaken limits on dark matter annihilation in the Sun. On the direct detection side, we show that models in which sterile neutrinos form part of a larger hidden sector can lead to interesting new signatures of solar sterile neutrinos scattering on electrons or nuclei. On the one hand, these signatures provide a new application for dark matter detectors, on the other hand they are not always easy to distinguish from dark matter scattering signals.
ICTPICTPpio@ictp.it

Europe/RomeWe study relaxation of an excited electron in the conduction band of intrinsic graphene at zero temperature due to production of interband electron-hole pairs by Coulomb interaction. The electronic band curvature, being anisotropic because of trigonal warping, is shown to suppress relaxation for a range of directions of the initial electron momentum. For other directions, relaxation is allowed only if the curvature exceeds a finite critical value; otherwise, a non-decaying quasiparticle state is shown to exist.ICTPICTPpio@ictp.it

Europe/RomeSpatial inhomogeneities, e.g. dislocations or impurities are inevitable features of realistic systems. In condensed matter physics, the dynamics of disorder is usually slow compared to experimental time scales, thus inhomogeneities are well approximated by time-independent, quenched disorder. Although being a microscopic perturbation, quenched disorder may dramatically change the large-scale critical behavior of the system. A paradigmatic example is the zero temperature quantum phase transition of the quantum Ising model, where the system exhibits exotic, infinitely disordered critical behavior. Besides the quantum Ising model, there is a huge number of further interesting examples, such as the random walk in 1D, the 1D Hubbard model, the Mott metal-insulator transition in 2D, localization of a random polymer at an interface, random exclusion processes and trap models, driven lattice gases and reaction diffusion models, as well as a number of classical and quantum spin systems. In the understanding of the phenomena the strong disorder renormalization group (SDRG) method plays a crucial role, yielding exact analytical results in 1D. Unfortunately, in higher dimensional systems the method is only numerically applicable. In 2D this enabled to study only relatively small systems with a limited accuracy. In the experimentally important three dimensional case no quantitative results have been achieved.
In this talk I will give an overview about my analytical and numerical results concerning the SDRG method, leading to the first quantitative results in 3 (and higher) dimensions. The obtained results are directly applicable also for the contact process, which is a simple model of infection spreading.
ICTPICTPpio@ictp.it

Europe/RomeAbstract: We study the energy loss of a rotating infinitely massive quark moving, at constant velocity, through an anisotropic strongly- coupled N = 4 plasma from holography. It is shown that, similar to the isotropic plasma, the energy loss of the rotating quark is due to either the drag force or radiation with a continuous crossover from drag-dominated regime to the radiation dominated regime. We find that the anisotropy has a significant effect on the energy loss of the heavy quark, specially in the crossover regime. We argue that the energy loss due to radiation in anisotropic media is less than the isotropic case. Interestingly this is similar to analogous calculations for the energy loss in weakly coupled anisotropic plasma.ICTPICTPpio@ictp.it

Europe/RomeFounded over a century ago, statistical mechanics (SM) for systems in thermal equilibrium has been so successful that, nowadays, it forms part of our physics core curriculum. On the other hand, most of "real life" phenomena occur under non-equilibrium conditions.
Unfortunately, statistical mechanics for such systems is far from being well established. The goal of understanding complex collective behavior from simple microscopic rules (of evolution, say) remains elusive. As an example of the difficulties we face, consider predicting the existence of a tree from an appropriate collection of H,C,O,N,... atoms!
Over the last two decades, an increasing number of condensed matter theorists are devoting their efforts to this frontier. After a brief summary of the crucial differences between text-book equilibrium SM and non-equilibrium SM, I will give a bird's-eye view of some key issues, ranging from the "fundamental" to (a small set of) the "applied." The methods used also span a wide spectrum, from "easy" computer simulations to sophisticated field theoretic techniques. These will be illustrated in the context of an overview of our work, as well as a simple Ising model coupled to two thermal baths.
SISSA, Santorio Building, Room 5 (ground floor)ICTPpio@ictp.it

Europe/RomeThe hard-disk model has exerted outstanding influence on computational physics and statistical mechanics. Decades ago, hard disks were the first system to be studied by Markov-chain Monte Carlo methods and by molecular dynamics. It was in hard disks, through numerical simulations, that a two-dimensional melting transition was first seen to occur even though such systems cannot develop long-range crystalline order. Analysis of the system was made difficult by the absence of adequate simulation methods.
In recent years, we have developed a number of powerful Monte Carlo algorithms for hard disks and related systems. I will in particular show how the powerful event-chain Monte Carlo algorithm has allowed us to
show that hard disks melt with a first-order transition from the liquid to the hexatic and a continuous transition from the hexatic to the solid. I will finish with discussions on the general theory of two-dimensional melting and on the generalizations of the event-chain algorithm.
ICTPICTPpio@ictp.it

Europe/RomeThe study of complex systems is limited by the fact that only few variables are accessible for modeling and sampling, which are not necessarily the most relevant ones. In addition, empirical data typically under sample the space of possible states.
We study a class of complex systems, which are systems of many interacting degrees of freedom, which are known only in part, that optimize a given function. We show that the information that a sample contains on the behavior of the system is quantified by the entropy of the frequency with which different states occur. This allows us to characterize the properties of maximally informative samples:
In the under-sampling regime, the most informative frequency size distributions have power law behavior and Zipf's law emerges at the crossover between the under sampled regime and the regime where the sample contains enough statistics to make inference on the behavior of the system. These ideas are illustrated in some applications, showing that they can be used to identify relevant variables or to select most informative representations of data, e.g. in data clustering.
ICTPICTPpio@ictp.it

Europe/RomeRandom Matrix Theory was initially developed to explain the eigen-energy distribution of heavy nuclei. It has become clear by now that its domain of application is much broader and extends to very different fields such as number theory and quantum chaos, just to cite a few. In particular, it has been conjectured—and proved or verified in some special cases—that quantum ergodic (or chaotic) systems are characterized by eigen-energies statistics in the same universality class of random matrices and by eigen-functions that are delocalized over the configuration space. On the contrary, non-ergodic quantum systems, such as integrable models, are expected to display a Poisson statistics of energy levels and localized wave-functions. Starting from Anderson’s pioneering papers, similar properties have also been studied for electrons hopping in a disordered environment. Remarkably, also in this case, similar features of the energy-level statistics have been found. All that has lead to the conjecture that delocalization in configuration space, ergodicity and level statistics are intertwined properties.
In this talk we revisit the old problem of non-interacting electrons hopping on a Bethe lattice with on-site disorder. By using numerical simulations, the cavity method and mapping to directed polymers in random media we unveil the existence of an intermediate phase in which wave-functions are delocalized but the energy-level statistics is Poisson. This new phase, in which the system is non-ergodic but delocalized, may play an important role in several fields from random matrix theory to strongly interacting quantum disordered systems, in particular it could be related to the non-ergodic metallic phase conjectured to exist in the context of Many-Body Localization.
ICTPICTPpio@ictp.it

Europe/RomeAbstract: The observational data provided by Planck satellite indicates some deviations from the statistical isotropy, which is one of the fundamental assumptions of the standard model of cosmology. These statistical anisotropies may be achieved by introducing some vector fields during inflation. In this talk, first I consider an inflationary model with U(1) gauge fields and charged scalar field. I show that there exists attractor solution where the anisotropies produced during inflation become comparable to the slow-roll parameters. Then, using the in-in formalism, I obtain the correction to the primordial power spectrum due to this anisotropic sources. Finally, I present another method ,delta N formalism, for calculating the curvature perturbations in anisotropic background which is an extension of usual approach for FRW background.ICTPICTPpio@ictp.it

Europe/RomeI will discuss the fundamental equivalence between thermodynamic inefficiency, measured by dissipation, and information processing inefficiency. The dynamics of any system responding to a stochastic environmental signal can be interpreted as computing an implicit model of the driving signal. The system’s state retains information about past environmental fluctuations, and a fraction of this information is predictive of future fluctuations. The remaining nonpredictive information reflects model complexity that does not improve predictive power, and thus represents the inefficiency of the model. We find that instantaneous nonpredictive information: 1) is proportional to the work dissipated due to environmental change; 2) provides a lower bound on the total dissipated work when summed over the length of a driving protocol; 3) augments the lower bound on heat generated due to information erasure (Landauer's principle). Our results hold far from thermodynamic equilibrium and are thus applicable to a wide range of systems, including biomolecular machines, and potential future nano computing devices. These results highlight a profound connection between the effective use of information and efficient thermodynamic operation: any system constructed to keep memory about its environment, and to operate with maximal energetic efficiency, has to be predictive. http://prl.aps.org/abstract/PRL/v109/i12/e120604SISSA, Santorio Building, Room 128 (1st Floor)ICTPpio@ictp.it

Europe/RomeNon-linear sound is an extreme phenomenon typically observed in solids after violent explosions. But granular media are different. Right when they unjam, these fragile and disordered solids exhibit vanishing elastic moduli and sound speed, so that even tiny mechanical perturbations form supersonic shocks. Here, we perform simulations in which two-dimensional jammed granular packings are continuously compressed, and demonstrate that the resulting excitations are strongly nonlinear shocks, rather than linear waves. We capture the full dependence of the shock speed on pressure and compression speed by a surprisingly simple analytical model. We also treat shear shocks within a simplified viscoelastic model of nearly-isostatic random networks comprised of harmonic springs. In this case, anharmonicity does not originate locally from nonlinear interactions between particles, as in granular media; instead, it emerges from the global architecture of the network. As a result, the diverging width of the shear shocks bears a nonlinear signature of the diverging isostatic length associated with the loss of rigidity in these floppy networks.SISSA, Santorio Building, Room 4 (ground floor)ICTPpio@ictp.it

Europe/RomeI will discuss the Dirac quasiparticles in the lattice systems of electrons, exemplified by graphene, in the presence of topological defects of the allowed order parameters. These orders appear as possible mass terms in the Dirac equation, and their topological defects have been known to carry non-trivial quantum numbers such as fractionalized charge since the work of Jackiw and Rebby in 1976. In the talk I will discuss their additional internal degree of freedom: irrespectively of the nature of orders that support the defect, an extra mass-order-parameter spontaneously emerges in the defect's core. The determination of the quantum state of the topological defect in Dirac systems turns out to be an interesting problem in the (real) representation theory of Clifford algebras; with the Clifford algebra C(2,5) playing a fundamental role in graphene, for example. Ultimately, the particle-hole symmetry restricts the defects to always carry the quantum numbers of a single effective "isospin" - 1/2, quite independently of the values of their electric charge or true spin. Examples of this new degree of freedom in graphene and other Dirac-like systems, such as graphene bilayers or d-wave superconductors will be given.ICTPICTPpio@ictp.it

Europe/RomeThis will be the first of a series of approximately 4 one-hour lectures.
The subject of these lectures is enumerative geometry of curves on algebraic surfaces and its relation to Hilbert schemes of points, real algebraic geometry and tropical geometry.
The generating function of the Euler numbers of Hilbert schemes of points on curves has been used by Pandharipande and Thomas to give a mathematical definition of Gopakumar-Vafa invariants, and by Kool-Shende-Thomas to give a proof of a conjecture of mine which describes the generating function of the numbers of δ-nodal singular curves in a linear system of dimension δ on any surface. Shende and me gave a conjectural refinement of this conjecture. Here the number of curves is replaced by a polynomial, whose meaning is still mysterious, but it can be seen to be related to tropical geometry and real algebraic geometry. In this series of lectures we want to explain this circle of ideas, and also use the opportunity to introduce a number of important concepts and techniques, generating functions, cobordism ring, localization, Severi degrees, Welschinger invariants, tropical geometry, Heisenberg algebra.ICTPICTPpio@ictp.it

Europe/RomeAbstract. The mini-landscape of heterotic string compactifications is a set of hundreds of T^6/Z_{6II} orbifold models with the spectrum of the minimal supersymmetric standard model. Those constructions have an anomalous U(1) gauge symmetry that generates a D-term, which has to be canceled by assigning vevs to scalars fields in order to preserve the N=1 supersymmetry. This process breaks global discrete symmetries, decouples exotic states and reduces the gauge sector to give realistic constructions. The vevs of fields located at the orbifold singularities can parametrize the blow-up of the singularities to a generic smooth Calabi-Yau 3-fold. We will start with a review of the heterotic orbifold compactifications and their blown-up counterparts. The smooth CY are studied by a dimensional reduction of the 10d N=1 supergravity theory coupled to super Yang-Mills with an abelian gauge flux in the internal dimensions. I then present the deformation of a T^6/Z_{6II} compactification with MSSM-like spectrum by vevs. I establish the correspondence between the deformed orbifold and a smooth CY 3-fold by identifying the blow-up modes, matching the massless spectrum and comparing the 4d anomaly cancellation mechanism.ICTPICTPpio@ictp.it

Europe/RomeAbstract. In this talk, I will describe how to test composite Higgs models at LHC by searching for top partners, in a simple and sistematic way. In the first part, I will show how to build effective lagrangians capturing the relevant features with a small number of parameters. In the second part, I will explore some of the rich phenomenology and use the experimental data to derive bounds on top partners. I will conclude by highligthing the open questions and the room for improvement.
ICTPICTPpio@ictp.it

Europe/RomeIn this talk I will review general non-adiabatic theories of two- and three- level crossings subject to fast and slow Gaussian noise.
The applications to recent experiments on Landau - Zener interferometry in double/triple quantum dots and superconducting qubits will be discussed.
ICTPICTPpio@ictp.it

Europe/RomeAbstract. Using holography we study the imaginary of the heavy quark anti-quark (dipole) potential in the anisotropic plasma at finite temperature. The anisotropic plasma is a deformation of N=4 SYM theory by adding a Theta-term depending on the anisotropy direction to the action. From gravity side the deformation can be thought as generated from a back-reacting number of D7 branes wrapping the internal 5-sphere and two of the spatial directions (transverse directions) in the space-time. The imaginary part of the potential creates a thermal width and by comparing the results with isotropic case we show that the thermal width in the anisotropic plasma is larger than the isotropic case. The thermal width is a function of the angle between the dipole and anisotropy direction and we show that the thermal width in anisotropy direction is larger than the thermal width in transverse direction.ICTPICTPpio@ictp.it

Europe/RomeWe experimentally study the transport process of ultracold fermionic atoms through a mesoscopic, quasi two-dimensional channel connecting macroscopic reservoirs. By observing the current response to a bias applied between the reservoirs, we directly access the resistance of the channel in a manner analogous to a solid state conduction measurement. The resistance is further controlled by a gate potential reducing the atomic density in the channel, like in a field effect transistor. In this setup, we study the flow of a strongly interacting Fermi gas, and observe a striking drop of resistance with increasing density in the channel, as expected at the onset of superfluidity. The resistance is compared to that of an ideal Fermi gas in the same geometry, which shows an order of magnitude larger resistance, originating from the contact resistance between the channel and the reservoirs. We extended this investigation to disordered superfluids and provide evidences for a disorder-induced breakdown of superfluidity.ICTPICTPpio@ictp.it

Europe/RomeASSOCIATED ACTIVITIES:
The workshop will be run in collaboration with the preceding School on Modelling Tools and Capacity Building in Climate and Public Health (15 April - 1 May, smr2453).
Participants can also apply to attend this earlier School. Attendance at both workshops is not mandatory, each workshop is designed to be self-contained. However, during the first three days, the School and this Workshop will integrate by focusing the lectures on topics of common interest.
The Workshop is co-sponsored by IUGG Trieste - ItalyICTPpio@ictp.it

Europe/RomeAbstract: This talk will is about work with Ben McReynolds and Matt Stover on variations of the higher Lehmer conjecture of F. Rodriguez Villegas. These conjectures concern the unit groups of algebraic number fields. I will make a connection between these conjectures and the Cheeger constants of certain flat manifolds which are naturally related to units. Cheeger constants measure the size of the minimal codimension one submanifold which cuts the original manifold into two disjoint pieces of equal volume.ICTPICTPpio@ictp.it

Europe/RomeGAMMA-400 is a Russian-based space mission devoted to the study of the Universe at the highest gamma-ray and electron energies detectable by space satellites. The main goal is search of indications of Dark Matter. Other items concern the study of high energy cosmic –ray electrons and nuclei. This unique combination will put GAMMA-400 at the forefront of research in the next decade.Trieste - ItalyICTPpio@ictp.it

Europe/RomeWe discuss the formation of bound states made of two interacting atoms moving in a one dimensional (1D) quasi-periodic optical lattice.
The underlying hamiltonian is the Aubry-André model with additional on-site interactions.
We derive the quantum phase diagram for localization of both attractively and repulsively bound pairs. We calculate the pair binding energy and show analytically that its behavior as a function of the interaction strength depends crucially on the nature -extended, multifractal, localized- of the single-particle atomic states. Experimental implications of our results are discussed.
Ref: G. Dufour, G. Orso, Phys. Rev. Lett. 109, 155306 (2012)
ICTPICTPpio@ictp.it

Europe/RomeAbstract:
We address the problem of the conditions under which an endomorphism(non-invertible map) having a dense orbit ensures that a sufficiently close perturbed map also exhibits a dense orbit.
In this context, we give sufficient conditions, which cover a large class of examples, for endomorphisms on the n-dimensional torus to be robustly transitive: the endomorphism must be volume expanding and any large connected arc must contain a point such that its future orbit belongs to an expanding region.
(Joint work with E. Pujals)
If we have enough time, I will show some ergodic properties for a generic subset of this class of maps. More concretely, the existence of interesting measures such as ergodic expanding invariant measures with full support and exhibiting exponential decay of correlations.
(Joint work with V. Pinheiro and P.Varandas)
Some examples will be shown.
ICTPICTPpio@ictp.it

Europe/RomeThis is a joint seminar between the Condensed Matter (Statistical Physics) and Applied Physics Sections. You will be especially welcome if you are visiting the Centre, or another Trieste Institute, as Associate Members, TRIL Fellows, or if you are from Affiliated Institutes in the various areas of this stimulating interdisciplinary event.
The summary of the seminar is available at:
http://www.ictp.it/~chelaf/ss317.htmlICTPICTPpio@ictp.it

Europe/RomeColonies of motile microorganisms, the cytoskeleton and its components, cells and tissues have much in common with soft condensed matter systems
(i.e. liquid crystals, amphiphiles, colloids etc.), but also exhibit behaviors that do not appear in inanimate matter and that are crucial for biological functions. These unique properties arise when the constituent particles are active: they consume energy from internal and external sources and dissipate it by moving through the medium they inhabit. In this talk I will give a brief introduction to the notion of "active matter" and present some recent results on the hydrodynamics of active nematics suspensions in two dimensions.
SISSA, Santorio Building room 128 (1st floor) ICTPpio@ictp.it

Europe/RomeIn this seminar we survey discrete time, multi period, sequential investment strategies for financial markets.
Under memoryless assumption on the underlying process generating the asset prices the Best Constantly Rebalanced Portfolio is studied, called log-optimal portfolio, which achieves the maximal asymptotic average growth rate. For generalized dynamic portfolio selection, when asset prices are generated by a stationary and ergodic process, universally consistent empirical methods are shown, using current principles of nonparametric regression estimation and machine learning algorithms.
The empirical performance of the methods are illustrated for NYSE data.
ICTPICTPpio@ictp.it

Europe/RomeA substantial magnetodielectric effect is usually an indication of coupled magnetic and elastic order, such as is found in the multiferroics. However, here I will show that magnetism is not necessary to produce either a magnetoresistance or a magnetocapacitance when the material is inhomogeneous. From exact calculations and numerical simulations of metal-dielectric composites, I find a characteristic dielectric resonance that sensitively depends on magnetic field. I will discuss how this behaviour has already been observed experimentally in some materials. ICTPICTPpio@ictp.it

Europe/Rome(This is the second of a series of approximately 4 lectures of 60 minutes).
The subject of these lectures is enumerative geometry of curves on algebraic surfaces and its relation to Hilbert schemes of points, real algebraic geometry and tropical geometry.
The generating function of the Euler numbers of Hilbert schemes of points on curves has been used by Pandharipande and Thomas to give a mathematical definition of Gopakumar-Vafa invariants, and by Kool-Shende-Thomas to give a proof of a conjecture of mine which describes the generating function of the numbers of δ-nodal singular curves in a linear system of dimension δ on any surface. Shende and me gave a conjectural refinement of this conjecture. Here the number of curves is replaced by a polynomial, whose meaning is still mysterious, but it can be seen to be related to tropical geometry and real algebraic geometry. In this series of lectures we want to explain this circle of ideas, and also use the opportunity to introduce a number of important concepts and techniques, generating functions, cobordism ring, localization, Severi degrees, Welschinger invariants, tropical geometry, Heisenberg algebra.ICTPICTPpio@ictp.it

Europe/RomeAbstract. The velocity distribution function (VDF) of Dark Matter (DM) in Milky Way is determined directly from observational data of the Galaxy. This is done by "inverting" --- using Eddington's method --- the Navarro-Frenk-White universal density profile of the DM halo of the Galaxy, the parameters of which are determined from a recently compiled set of observational data on the Galaxy's rotation curve extended to distances well beyond the visible edge of the disk of the Galaxy. The derived most-likely local isotropic VDF strongly differs from the Maxwellian form assumed in the "Standard Halo Model" (SHM) customarily used in the analysis of the results of direct-detection experiments. The astrophysical "g-factor" that determines the effect of the DM VDF on the expected event rate in a direct-detection experiment can be lower for the observational VDF than that for the closest Maxwellian VDF by as much two orders of magnitude at the lowest DM mass threshold of a typical experiment.
ICTPICTPpio@ictp.it

Europe/RomeAbstract:
Quantum cohomology ring of a smooth projective variety X is a certain deformation of its usual cohomology ring. This structure was introduced at the begging of 90's motivated by works of string theorists. Later on an analogue of the quantum product was defied in the K-theory. In this talk I will describe a way to define an analogue of the quantum product on the derived category of X.
ICTPICTPpio@ictp.it

Europe/RomeDue to its simplicity and numerical efficiency, density functional theory (DFT) is the most popular approach for calculating the electronic structure of large molecules and materials. Nevertheless, the accuracy of DFT is not always satisfactory and the search for improved approximations that avoid self-interaction and capture strong electron correlations faces severe difficulties. In this talk I will present an alternative approach in which the one- and two-particle density matrices needed to compute the ground-state energy, are explicit functionals of the natural spin orbital states and their joint occupation probabilities. The scheme is parameter-free and not affected by self-interaction error. In its simplest formulation, restricted to the seniority zero sector of the many-particle Hilbert space, it has the same scaling of Hartree-Fock theory. Yet, it describes strong correlations as demonstrated by calculating the dissociation energy curves of diatomic molecules and linear chains of hydrogen atoms. Improved approximations that retain polynomial cost but are not limited to seniority zero will be also discussed.ICTPICTPpio@ictp.it

Europe/RomeFor quantum systems specified by a given density matrix at initial time, a generating functional for real-time correlation functions can be written down using the Schwinger-Keldysh closed time path. This can be used to construct a nonequilibrium functional renormalization group along similar lines as for Euclidean field theories in thermal equilibrium. Important differences include the absence of a fluctuation-dissipation relation for general out-of-equilibrium situations. The nonequilibrium renormalization group takes on a particularly simple form at a fixed point, where the corresponding scale-invariant system becomes independent of the details of the initial density matrix. This can be used to derive a hierarchy of fixed point solutions with increasing complexity from vacuum and thermal equilibrium to nonequilibrium. The application to dynamic critical phenomena and the phenomenon of turbulence in quantum field theory will be discussed.ICTPICTPpio@ictp.it

Europe/Rome(This is the third of a series of approximately 4 lectures of 60 minutes).
The subject of these lectures is enumerative geometry of curves on algebraic surfaces and its relation to Hilbert schemes of points, real algebraic geometry and tropical geometry.
The generating function of the Euler numbers of Hilbert schemes of points on curves has been used by Pandharipande and Thomas to give a mathematical definition of Gopakumar-Vafa invariants, and by Kool-Shende-Thomas to give a proof of a conjecture of mine which describes the generating function of the numbers of δ-nodal singular curves in a linear system of dimension δ on any surface. Shende and me gave a conjectural refinement of this conjecture. Here the number of curves is replaced by a polynomial, whose meaning is still mysterious, but it can be seen to be related to tropical geometry and real algebraic geometry. In this series of lectures we want to explain this circle of ideas, and also use the opportunity to introduce a number of important concepts and techniques, generating functions, cobordism ring, localization, Severi degrees, Welschinger invariants, tropical geometry, Heisenberg algebra.ICTPICTPpio@ictp.it

Europe/RomeAbstract. We will briefly review the strong CP problem and the solution proposed by Peccei and Quinn, the existence of a new degree of freedom that restores C and P conservation in the colour sector: the axion. Then we will review the cosmology of axions focusing on their role as dark matter, and the perspectives for its discovery.ICTPICTPpio@ictp.it

Europe/RomeAbstract:
We consider a family of adapted complex structures on the cotangent bundle of a Lie group and find the BKS pairing relating the corresponding half-form quantisation. We show that the resulting bundle of quantum Hilbert spaces over the space of polarisations is flat. The vertical polarisation as a limit of complex polarisations yields the coherent state transform (or the Segal-Bargmann-Hall transform). We show that there is another limit of the complex polarisations that corresponds to the Peter-Weyl theorem.
This is a joint work with W. Kirwin.
ICTPICTPpio@ictp.it

Europe/RomeI review the concept of ultra-cold atoms as universal quantum simulators for quantum many body systems, focusing on motivations, main targets and open problems. As a realistic example I then describe a setup of ultracold fermionic mixtures in optical lattices able to host superfluid phases with symmetry obtained by locking independent invariance groups of the normal state. Due to their peculiar symmetry, these phases can also show exotic soliton structures, as vortices with semi-integer flux and gapless non-Abelian Goldstone modes localized on them. The origin of the non-abelianity, the braiding properties, the mechanism and the consequences of fractionality for such vortices are discussed. The scenario proposed displays remarkable similarities to what arises in ultra-dense QCD matter, as in the core of some neutron stars. A discussion about the experimental detection of locked phases and non-abelian fractional vortices is as well provided.ICTPICTPpio@ictp.it

Europe/RomeIn this talk I will discuss applications of first principles electronic structure calculations and molecular dynamics simulations to understand materials properties and reaction mechanisms relevant to photocalysis and energy applications. Examples will focus on the surface properties of TiO2, a widely used photocatalyst capable of splitting water in O2 + H2, and hydrogen production from water by the active site of an enzyme of hydrogen-producing bacteria, the di-iron hydrogenase, linked to a pyrite electrode.SISSA, Santorio Building, Room 128 (1st Floor) ICTPpio@ictp.it

Europe/RomeWe suggest a new perspective on the Cosmological Constant Problem by scrutinizing its standard formulation. In classical and quantum mechanics without gravity, there is no definition of the zero point of energy. Furthermore, the Casimir effect only measures how the vacuum energy changes as one varies a geometric modulus. This leads us to propose that the physical vacuum energy in a Friedman-Lemaitre-Robertson-Walker expanding universe only depends on the time variation of the scale factor $a(t)$. Equivalently, requiring that empty Minkowski space is gravitationally stable is a principle that fixes the ambiguity in the zero point energy. On the other hand, if there is a meaningful bare cosmological constant, this prescription should be viewed as a fine-tuning. We describe two different choices of vacuum, one of which is consistent with the current universe consisting only of matter and vacuum energy. The resulting vacuum energy density is constant in time and approximately kc2 H02, where kc is a momentum cut-off and H0 is the current Hubble constant; for a cut-off close to the Planck scale, values of vacuum energy density in agreement with astrophysical measurements are obtained. Another choice of vacuum is more relevant to the early universe consisting of only radiation and vacuum energy, and we suggest it as a possible model of inflation.SISSA, Santorio Building, Room 128 (1st Floor)ICTPpio@ictp.it

Europe/RomeAbstract. I introduce a class of holographic systems describing chemically unbalanced Fermi mixtures at strong coupling. Such systems feature interesting intertwined “spin-electric” transport and superconducting properties. After illustrating the minimal model, I enlarge the perspective including multiple order parameters and address the study of competition/enhancement of multiple orderings in a strongly coupled context by means of AdS/CFT correspondence.ICTPICTPpio@ictp.it

Europe/RomeIn the summer of 2012, a series of scandals broke out around the largest, systemically most important banks of the world. In most cases, the roots and practice of misdeeds (Libor rigging, violations of sanctions, money laundering, mis-selling of fake products, tax fraud, insider trading, etc.) go back several years. Regulators imposed record fines on the banks, in a few cases started criminal procedures against the most incriminated players, and a deluge of lawsuits was launched. The regulators raised questions about the responsibility of rating agencies and consultants, but in some cases the scandals shed a dubious light on the regulators themselves, as well as on the British and US governments, and also the American Congress.
The talk reviews some of the elements of this series of scandals, and tries to draw some conclusions for regulation.
ICTPICTPpio@ictp.it

Europe/RomeAbstract: I will briefly review the higher spin generalization of the well known equivalence between SL(2)xSL(2) CS gauge theory and 3D Einstein Gravity with negative cosmological constant. Generalizations of BTZ black holes can be found in these theories but the presence of horizon is not a gauge dependent statement. Apparently there is always a gauge where the geometry looks like a domain wall configuration interpolating between two different AdS's and different asymptotic W-symmetry algebras. A pretty much detailed CFT dual perspective can be decoded just from the HS bulk analysis. ICTPICTPpio@ictp.it

Cosponsor(s):
European Women in Mathematics (EWM); INDAM (GNAMPA) and (GNFM); Department of Mathematics and Geosciences, University of Trieste; Department of Mathematics, University of Torino; Department of Mathematics, University of L'Aquila; SISSA; COMPOSITIO MATHEMATICA.

Europe/RomeMore than 10 years ago, it was realized that mean field glassy dynamics, with the emergence of aging and effective temperatures, can be understood as quasi-equilibrium exploration of configuration space. The formalization of this notion, only recently proposed, defines a Markov chain where short times are coarse grained, and subsequent configurations are chosen according to a constrained Boltzmann distribution.
In mean field spin glasses, this pseudodynamic rule admits, in the long time limit, a description leading to glassy solutions identical to the ones corresponding to real (Langevin) dynamics. The treatment of the pseudodynamics through replicas unveils a longly suspected relation between replicas and the supersymmetry of the Langevin equation.
The application of the formalism to liquids avoids the difficulties related to short time conservation laws, and allows to use equilibrium approximation schemes of liquid theory to study long time dynamics. The scheme is applied to a closure scheme of hierarchical equations recently proposed by Szamel and to liquids in the hypernetted chain (HNC) approximation. It is shown that the former case leads to the standard Mode Coupling Theory (MCT) equations of Gœtze, thus giving an interpretation of it. The second case also gives rise to MCT-like equations, but in a framework where, differently from MCT that requires the input of equilibrium structure factors, static equilibrium and dynamical quantities are computed in a unified consistent framework.
Refs. SF and G. Parisi, JSTAT P02003 (2013), SF, G. Parisi and P. Urbani, arXiv:1212.4291
ICTPICTPpio@ictp.it

Europe/Rome I will start with the idea of electronic shell models as proposed for simple metal clusters, and show how this leads to the idea of superatoms. I will then present our work on 3d transition metal (TM) doped alkali and alkaline earth clusters and show how the ideas of electronic shell models play out in these. This will lead us to magnetic superatoms. I will also point out how a subtle interplay of crystal field effect and exchange coupling leads to enhanced stability for certain TM-alkaline earth clusters, and leads to new magnetic superatoms in this series. Time permitting, I will present some of our recent results on TM-doped aluminum clusters and will argue that aromaticity rather than shell models plays a role in these clusters.ICTPICTPpio@ictp.it

Europe/RomeRecently, Coulomb drag measurements have been performed in graphene, usually in the presence of magnetic fields as well. In this work we calculate the magneto-drag and the Hall-drag resistivity at finite temperature for two graphene monolayers by solving the quantum kinetic equation. The presented theory is valid in the hydrodynamic regime, which is dominated by inelastic scattering. The microscopic formulation supports a phenomenological Drude-like picture which for large concentrations equals the usual Drude form, and for small concentration an effective two-band-Drude equation. Our theory allows for a qualitative description for arbitrary chemical potentials. An emphasis is put on the Hall-drag which is absent when derived from the standard Drude equation. We show that the Hall-drag vanishes along the line of opposite carrier concentration in the layers, but we also identify non trivial concentrations at which the Hall-drag vanishes.ICTPICTPpio@ictp.it

Europe/RomeThe subject of these lectures is enumerative geometry of curves on algebraic surfaces and its relation to Hilbert schemes of points, real algebraic geometry and tropical geometry.
The generating function of the Euler numbers of Hilbert schemes of points on curves has been used by Pandharipande and Thomas to give a mathematical definition of Gopakumar-Vafa invariants, and by Kool-Shende-Thomas to give a proof of a conjecture of mine which describes the generating function of the numbers of δ-nodal singular curves in a linear system of dimension δ on any surface. Shende and me gave a conjectural refinement of this conjecture. Here the number of curves is replaced by a polynomial, whose meaning is still mysterious, but it can be seen to be related to tropical geometry and real algebraic geometry. In this series of lectures we want to explain this circle of ideas, and also use the opportunity to introduce a number of important concepts and techniques, generating functions, cobordism ring, localization, Severi degrees, Welschinger invariants, tropical geometry, Heisenberg algebra.ICTPICTPpio@ictp.it

Mathematics

Cosponsor(s):
International School for Advanced Studies (SISSA), National Research University Higher School of Economics - Moscow (NRU HSE) and Steklov Mathematical Institute of the Russian Academy of Science (MIRAS)

Activity

Europe/RomeAbstract: Oscillons are long-lived, localized excitations of nonlinear scalar fields which may be copiously produced during preheating after inflation, leading to a possible oscillon-dominated phase in the early Universe. We investigate the stochastic gravitational wave background associated with an oscillon-dominated phase. An isolated oscillon is spherically symmetric and does not radiate gravitational waves and we show that the flux of gravitational radiation generated by pair-wise (and higher order) interactions is very small. However, a significant stochastic gravitational wave background may be generated during preheating itself, and in this case the characteristic size of the oscillons is imprinted on the gravitational wave power spectrum, which has multiple, distinct peaks.
ICTPICTPpio@ictp.it

Europe/RomeAbstract. The dynamics of quantum fields in de Sitter space is radically different from the flat space case. For light scalar fields, perturbation theory is plagued by infrared divergences which require resummation techniques. Existing such techniques, developed for flat space quantum field theory (QFT) are difficult to implement in curved spaces mainly because of the phenomenon of gravitational redshift. I present recent work on this topics concerning a new formulation of QFT in de Sitter space which exploits as much as possible de Sitter symmetries and the power of a momentum representation. This p-representation solves the gravitational redshift problem and allows one to formulate standard resummation techniques of QFT in an efficient way. I discuss recent applications concerning the calculation of field correlators and the issue of spontaneous symmetry breaking in de Sitter space.ICTPICTPpio@ictp.it

Europe/RomeCareful transport measurements near the superconductor-insulator transition in amorphous indium-oxide reveal a symmetry relating states in the insulator to those in the superconducting phase. I will discuss this symmetry and its consequences, and show that it is violated upon entering
the strong insulator at low temperatures.
ICTPICTPpio@ictp.it

Europe/RomeAbstract: We calculate the relaxation rate of a scalar field in a plasma of other scalars and fermions with gauge interactions using thermal quantum field theory. It yields the rate of cosmic reheating, which determines the temperature of the “hot big bang” in inflationary cosmology. The total rate originates from various processes, including decays and inverse decays as well as Landau damping by scatterings. We pay special attention to the temperature dependence of the phase space due to the modified dispersion relations in the plasma. We find that it can have a drastic effect on the efficiency of perturbative reheating, which depends on the way particles in the primordial plasma interact. For some interactions thermal masses can effectively close the phase space for the dominant dissipative processes and thereby impose an upper bound on the reheating temperature. In other cases they open up new channels of dissipation, hence increase the reheating temperature. At high temperatures we find that the universe can even be heated through couplings to fermions, which are often assumed to be negligible due to Pauli-blocking. ICTPICTPpio@ictp.it

Activity

Europe/RomeWe report on our recent progress regarding classes of materials which exhibit chiral triplet and singlet superconductivity, where topologically nontrivial
pairing phenomena can emerge. Specifically, motivated by recent experimental advances, we show that graphene doped to the van Hove regime can give rise to a plethora of interesting ordering instabilities such as spin density wave and superconductivity. As a function of system
parameters such as doping and range of Coulomb
interaction, we explain which instability is favored by the system, and analyze the effect of long-range interactions on superconductivity giving rise to a competition
between singlet d+id and triplet f wave. We further
report on our investigations of Cobaltate superconductors where we believe the experimental evidence can be reconciled by an anisotropic d+id superconducting gap.
We also outline our work in progress for other compounds such as strontium ruthenate and SrPtAs which we believe
are promising to stabilize such interesting topological superconducting states of matter.
ICTPICTPpio@ictp.it

Europe/RomeAbstract. Anthropological evidence shows a rather recent emergence of the modern cognitive human within a genetic and anatomic already evolved homo-sapiens. I will describe a proposition for the mind-brain mechanism that could underly that transition, as well as the ongoing work to identify and observe it by testing humans in laboratory conditions.ICTPICTPpio@ictp.it

Europe/RomeThe subject of these lectures is enumerative geometry of curves on algebraic surfaces and its relation to Hilbert schemes of points, real algebraic geometry and tropical geometry.
The generating function of the Euler numbers of Hilbert schemes of points on curves has been used by Pandharipande and Thomas to give a mathematical definition of Gopakumar-Vafa invariants, and by Kool-Shende-Thomas to give a proof of a conjecture of mine which describes the generating function of the numbers of δ-nodal singular curves in a linear system of dimension δ on any surface. Shende and me gave a conjectural refinement of this conjecture. Here the number of curves is replaced by a polynomial, whose meaning is still mysterious, but it can be seen to be related to tropical geometry and real algebraic geometry. In this series of lectures we want to explain this circle of ideas, and also use the opportunity to introduce a number of important concepts and techniques, generating functions, cobordism ring, localization, Severi degrees, Welschinger invariants, tropical geometry, Heisenberg algebra.ICTPICTPpio@ictp.it

Europe/RomeAbstract: In the first part of this talk I will review the invention of the eleven-dimensional supermembrane at the ICTP and how this has led to the concept of branes in string theory. In the second part I will review new insights in the classification of branes and why this suggests a new geometry underlying string theory.ICTPICTPpio@ictp.it

Europe/RomeAbstract. As is well known, hydrogen is the most abundant element in the Universe. Hydrogen in the low density intergalactic medium is photoionized by radiation from galaxies and other sources, while they remain in neutral form in very high density regions because of shielding. The evolution of neutral hydrogen through cosmic times passes through a number of interesting phases, namely, the dark ages, reionization and post-reionization epoch. Understanding each of these phases holds clue about the cosmology and galaxy formation in our Universe. In the talk, we will review our understanding of the physical processes related to cosmological distribution of neutral hydrogen and then present our recent results on these issues. We will also discuss prospects for using neutral hydrogen as strong probe of cosmology using future observational probes.ICTPICTPpio@ictp.it

Europe/RomeI will present theoretical results on induced
superconductivity in graphene covered by low
density of small (sub-micron) islands of
superconducting metal.
Then I present some of recently obtained
experimental data on graphene with tin islands
and discuss the comparison between the data and
the theory.
ICTPICTPpio@ictp.it

Europe/RomeThe subject of these lectures is enumerative geometry of curves on algebraic surfaces and its relation to Hilbert schemes of points, real algebraic geometry and tropical geometry.
The generating function of the Euler numbers of Hilbert schemes of points on curves has been used by Pandharipande and Thomas to give a mathematical definition of Gopakumar-Vafa invariants, and by Kool-Shende-Thomas to give a proof of a conjecture of mine which describes the generating function of the numbers of δ-nodal singular curves in a linear system of dimension δ on any surface. Shende and me gave a conjectural refinement of this conjecture. Here the number of curves is replaced by a polynomial, whose meaning is still mysterious, but it can be seen to be related to tropical geometry and real algebraic geometry. In this series of lectures we want to explain this circle of ideas, and also use the opportunity to introduce a number of important concepts and techniques, generating functions, cobordism ring, localization, Severi degrees, Welschinger invariants, tropical geometry, Heisenberg algebra.ICTPICTPpio@ictp.it

Europe/RomeAbstract: I will give a brief introduction about quantum squeezing, and discuss properties of some definitions of the spin squeezing parameter. Then I will show some recent results of our group for the time dependent squeezing parameter in different systems: Cavity QED, spin chains, and quantum corrals. ICTPICTPpio@ictp.it

Europe/RomeThe talk will discuss the dynamics of circle maps (orientation-preserving circle homeomorphisms (o.p.c.h)).
We will review the topological classification of these circle maps, namely the Poincare Classification and the Denjoy Theory. We will introduce the beautiful construction of the dynamical partition of the circle. We will review the connection between the concept of the Diophantine properties of the irrational rotation number of our map and the smooth classification of (sufficiently regular) circle maps (the so called "rigidity" theory), in the context of three important classes: diffeomorphisms, critical maps, and maps with a break point.
For circle maps with a break point, we will discuss two recent results that were obtained in the rigidity theory of circle maps with a break point.
The first main result is a proof that C^1 rigidity holds for circle maps with a break point for almost all irrational rotation numbers. This result is joint work with Kostya Khanin and Sasa Kocic.
The second main result has to do with the family of fractional linear transformation (FLT) pairs. An FLT-pair T is a circle homeomorphism that consists of two branches each of which is an FLT. Such a map can be viewed as a circle map with two neighbouring break points lying on the same orbit. For this family, C^1 rigidity holds for all irrational rotation numbers without any restriction (the so-called "robust rigidity").ICTPICTPpio@ictp.it

Europe/RomeFor more than 50 years we have known that photosynthetic systems harvest solar energy with almost unit quantum efficiency. However, recent experimental evidence of quantum coherence during the excitonic energy transport in photosynthetic organisms challenges our understanding of this fundamental biological function. Currently, and despite numerous efforts, the causal connection between coherence and efficiency is still a matter of debate. We show, through extensive simulations of quantum coherent transport on networks, that three dimensional structures characterized by centro-symmetric Hamiltonians are statistically more efficient than random arrangements. Moreover, we theoretical derive a general mechanism for highly efficient quantum transport through nite, disordered 3D networks. It relies on the interplay of disorder with centro-symmetry and a dominant doublet spectral structure, and can be controlled by proper tuning of only coarse-grained quantities. Photosynthetic light harvesting complexes are discussed as potential biological incarnations of this design principle.ICTPICTPpio@ictp.it

Europe/RomeAbstract: In compactifications of M-Theory, ADE singularities are expected to give rise to non-abelian gauge theories. In case the compactification manifold admits an torus fibration (this case is usually called `F-theory') such singularities become degenerations of the fibre. These degenerations have a nice classification due to Kodaira for complex surfaces, but no such classification exists in higher dimensions. In this talk, I will present some recent observations on the interplay between singular fibres and the effective low-energy physics in F-theory.ICTPICTPpio@ictp.it

Europe/RomeWe present a case for the realization of Majorana-like edge modes, through the quantum Ising (QI) dynamics, in the Rabi lattice. A Rabi lattice is an array of the Rabi quantum cavities where each cavity has a two-level atom (or a spin-1/2) coupled via dipole interaction to a single photon (bosonic) mode, and the inter-cavity coupling causes photon hopping. We show that the Rabi lattice model rigorously tends to the QI model in the limit of strong atom-photon coupling. This QI dynamics drives the para- to ferro-electric quantum phase transition in the Rabi lattice, and also guarantees two Majorana-like edge modes in the ordered phase on an open chain. We identify an observable signature of these modes, and check their stability against the detrimental perturbations such as a stray electric field. We find that the QI Majorana modes are not as fragile as one believed, despite no topological protection.ICTPICTPpio@ictp.it

Europe/RomeAbstract. We attempt an estimate for the distribution of the tensor-to-scalar ratio $r$ (the relative power of primordial gravitational waves from inflation) over the landscape of vacua in string theory. The dynamics of eternal inflation and quantum tunneling lead to a kind of democracy on the landscape, providing no bias towards large-field or small-field inflation regardless of the class of measure. The tensor mode fraction $r$ then follows the number frequency distributions of inflationary mechanisms of string theory over the landscape. We then determine the frequency of regions of small-field inflation in the Wigner landscape as an approximation to random supergravities/type IIB flux compactifications. We show that small-field inflation occurs exponentially more often than large-field inflation The tensor-to-scalar ratio $r$ is generically tied to the scale of inflation. For small-field models this is below current observational reach. However, we find small-field inflation to be dominated by the highest inflationary energy scales compatible with a sub-Planckian field range. Hence, we expect a typical $r\sim {\cal O}(10^{-3})$ currently undetectable in upcoming CMB measurements, but potentially detectable in a future dedicated B-mode space mission.ICTPICTPpio@ictp.it

Europe/RomeAbstract: Bertrand spacetimes (BSTs) are static, spherically symmetric solutions of Einstein's equations, that admit stable, closed orbits. Starting from the fact that to a good approximation, stars in the disc or halo regions of typical galaxies move in such orbits, we propose that, under certain physical assumptions, the dark matter distribution of some low surface brightness (LSB) galaxies can seed a particular class of BSTs. In the Newtonian limit, it is shown that for flat rotation curves, our proposal leads to an analytic prediction of the NFW dark matter profile.
ICTPICTPpio@ictp.it

Europe/RomeThis is the continuation of the Applied Physics Seminars. You will be especially welcome if you are visiting the Centre, or another Trieste Institute, as Associate Members, TRIL Fellows, or if you are from Affiliated Institutes in the various areas of Applied Physics.
The summary of the seminar is available at:
http://www.ictp.it/~chelaf/ss315.htmlICTPICTPpio@ictp.it

Europe/RomeWe will introduce the notions of the symplectic mean curvature flow and give some pinching conditions so that the symplectic mean curvature flow exists for long time and converges to a holomorphic curve.ICTPICTPpio@ictp.it

Europe/RomeAbstract: I review the knowledge of the Dark Matter distribution in our Galaxy in the light of recent experimental astrophysical data. I will focus on the determination of the Dark Matter density at the Sun's location and its uncertainties, interesting for direct detection experiments, and then review the constraints on the global spatial distribution, crucial for the indirect DM search especially towards the galactic center.
ICTPICTPpio@ictp.it

Europe/RomeAbstract: We show explicitly how the exact renormalization group equation of interacting vector models in the large N limit can be mapped into certain higher-spin equations of motion. The equations of motion are generalized to incorporate a multiparticle extension of the higher-spin algebra, which reflects the "multitrace" nature of the interactions in the dual field theory from the holographic point of view.ICTPICTPpio@ictp.it

Europe/RomeAbstract. The Dual Superconductor picture, proposed as a resolution for the prob- lem of Quark Confinement, predicts Flux Tubes connecting quarks. Evidence for such flux tubes in QCD has been unambiguously provided by Lattice Gauge Simulations. An algorithmic breakthrough by Luscher and Weisz permitted very accurate studies of the flux tube which showed that the sub- dominant term in ground state energy was characterstic of Bosonic Strings, the original candidates for explaining strong interactions.
Pushan Majumdar and myself carried out massive simulations using the Luscher-Weisz algorithm. We showed that even the next two higher order terms are exactly what is expected of a free bosonic string. Peter Matlock and myself subsequently proved this result analytically using the idea of effective string theories. I shall conclude by briefly reviewing the status of even higher order corrections as well as some implications of all these results.
ICTPICTPpio@ictp.it

Cosponsor(s):
In collaboration with: Aston Institute of Photonic Technologies, European Laboratory for Non-Linear Spectroscopy, Novosibirsk State University, Institute of Automation and Electrometry of Russian Academy of Science.

Europe/RomeThe purpose of this school is to provide a unique international educational experience aimed at building future leadership in managing nuclear energy programs from among promising young professionals from developing countries, particularly newcomer countries that seek to develop nuclear power or other nuclear applications, who show promise as future leaders of the nuclear industry, academia and public sector entities in their country.
It will enable the transfer of IAEA specific knowledge to Member States towards their capacity building efforts.
The School will consist of a series of keynote presentations by leading IAEA specialists on topics relevant to managing nuclear energy programs followed by practical sessions discussing the issues raised and difficulties envisaged.
All chosen participants will be expected to be actively involved in discussions, assigned projects, panel reviews and all school activities. Trieste - ItalyICTPpio@ictp.it

Activity

Applied Physics

Europe/RomeAbstract: The SuperCool inflation has the virtue of working "Naturally" at TeV scales and even much lower, which opens the possibility of using collider physics to probe inflation. In addition, the model introduces a new mechanism to end Old inflation. The Universe starts off hot and trapped in a false vacuum. The Universe supercools and inflates solving the horizon and flatness problems. The inflaton couples to a set of QCD like fermions. When the fermions' non-Abelian gauge group freezes, the Yukawa terms generate a tadpole for the inflaton, which removes the barrier. Inflation ends, and the Universe rapidly reheats. The model also can generate the necessary perturbations for inflation and can satisfy constraints from Plank.ICTPICTPpio@ictp.it

Mathematics

Europe/RomeAbstract
I will discuss the global phase diagram of the disordered Bose-Hubbard model in all dimensions controlled by the theorem of inclusions. In 1D, in the regime when strong disorder is more relevant than field quantization the superfluid--to--Bose-glass criticality is preceded by the prolonged logarithmically slow classical-field renormalization flow of the superfluid stiffness at mesoscopic scales. With the system compressibility remaining constant, the quantum nature of the system manifests itself only in the renormalization of dilute weak links. The transition point is still controlled by the proliferation of the instanton--anti-instanton pairs when the Luttinger liquid parameter equals 3/2, in accordance with the universal quantum scenario.ICTPICTPpio@ictp.it

Europe/RomeSCHOOL: 22 - 26 July 2013
WORKSHOP: 29 July - 2 August 2013
The purpose of the School is to provide the theoretical and computational tools to study the implications of the recent results from CMB experiments. It is intended for graduate students, as well as more senior non-expert researchers that are interested in these fields. The Workshop is devoted to the discussion of the experimental CMB results in all their aspects, their relation with other probes and the future prospects.
Trieste - ItalyICTPpio@ictp.it

Europe/RomeAbstract: IceCube has recently observed 2 cascade-like events at PeV energies. These are the highest energy neutrino events ever observed. In this talk I will present a phenomenological analysis of the IceCube data that explores the potential sources for these events. We predict that an efficient way to identify such sources is to look at lower energies, where more events are expected. Preliminary IceCube data already seems to confirm this expectation, and hints that this may be the first glimpse of high energy astrophysical neutrinos.
ICTPICTPpio@ictp.it

Europe/RomeWe obtain large deviation bounds for the measure of deviation sets associated to asymptotically additive and sub-additive potentials under some weak specification properties. Some applications to the study of the convergence of Lyapunov exponents are given.ICTPICTPpio@ictp.it

Europe/RomeWe consider chiral electrons moving along the 1D helical edge of a 2D topological insulator and interacting with a disordered chain of Kondo impurities. Assuming the electron-spin couplings of random anisotropies, we map this system to the problem of the pinning of the charge density wave by the disordered potential. This mapping proves that arbitrary weak anisotropic disorder in coupling of chiral electrons with spin impurities leads to the Anderson localization of the helical edge states [1].
[1] B.L. Altshuler, I.L. Aleiner, and V.I. Yudson, preprint arXiv: 1306.2626
ICTPICTPpio@ictp.it

Europe/RomeAbstract. We shall discuss some phenomenologically appealing features and challenges of heterotic orbifold compactifications, aiming at a theory of particles and cosmology. Obtaining globally consistent string constructions with properties akin to those of the (N)MSSM is made now trivial by using "The Orbifolder", an open-source computer code. The models constructed this way offer plenty of resources to possibly arrive at observable physics.ICTPICTPpio@ictp.it

Europe/RomeAbstract. A local and gauge invariant alternative version of QCD for massive fermions, will be presented. It is underlined that its action includes vertices which eventually could had been overlooked before for the consideration of gauge theories, since at first sight, they seem as breaking power counting renormalizability. However, the fact that those terms also modify the quark propagators, to become more convergent at large momenta, strongly suggests that theory is in fact renormalizable. Accepting this view, it also can be argued that all the four fermions terms constituting the Nambu-Jona-Lasinio models, could be included as counterterms in a slightly generalized renormalization procedure for massless QCD. The possible applications of these properties in massless SUSY models will be underlined.ICTPICTPpio@ictp.it

Europe/RomeAbstract
We discuss a model Kondo-type Hamiltonian representing an analytically tractable version of the model used by Yin et.al., Phys. Rev. B 86, 2399 (2012) to explain the non-Fermi liquid behavior of iron chalcogenides and ruthenates in an intermediate energy range. We consider a regime where a complete screening of the local degrees of freedom proceeds in two stages described by two characteristic energy scales T_K^orb >> E_0. The first scale marks a screening of the orbital degrees of freedom and the second one marks a crossover to the regime with coherent propagation of quasiparticles. We present analytical results for the specific heat and magnetic susceptibility at T << T_K^orb. ICTPICTPpio@ictp.it

Europe/RomeAbstract
Elastic backscattering of electrons moving along the helical edge is prohibited by time-reversal symmetry (TRS).
We demonstrate, however, that an ensemble of magnetic impurities may cause TRS-preserving quasi-elastic backscattering, resulting in interference effects in the conductance. The characteristic energy transferred in a backscattering event is suppressed due to the RKKY interaction of localized spins (the suppression is exponential in the total number of magnetic impurities). We predict the statistics of conductance fluctuations to differ from those in the conventional case of a one-dimensional system with quenched disorder.
Reference:
V.Cheianov, L.Glazman, Phys. Rev. Lett., 110, 206803. (2013)ICTPICTPpio@ictp.it

Europe/RomeIn this talk, we will present explicit examples of abelian surfaces with everywhere good reduction. One class of examples is connected with the Paramodularity Conjecture of Brumer-Kramer, which will be discussed in the process. This is joint work with Abhinav Kumar.ICTPICTPpio@ictp.it

Europe/RomeAbstract: In this talk I focus on the low temperature expansion of the first law of thermodynamics for near-extremal black holes and derive "laws of extremal black hole dynamics" and show that for extremal black holes with non-vanishing entropy, the leading order contribution yields an expression for their extremal entropy in agreement with the entropy function result and the Cardy formula for the entropy of a two dimensional chiral conformal field theory (CFT). When their entropy vanishes due to the vanishing of a one-cycle on the horizon, such leading contribution is always compatible with the first law satisfied by a BTZ black hole. These results are universal and consistent both with the presence of local AdS2 and AdS3 near horizon throats for extremal black holes and with the suggested quantum microscopic descriptions (AdS2/CFT1, Kerr/CFT and EVH/CFT).
ICTPICTPpio@ictp.it

Europe/RomeAbstract:
Titanium dioxide (TiO2¬) is a widely used material with many industrial applications. Because of the photocatalytic activity and environmental compatibility, it has tremendous potential applications in solar cells, dye industries, electronic devices, sensors and transformers. Density functional - pseudopotential calculations were performed to study the effect of hydrogen doping in bulk, and also H-doping and oxygen vacancy on electronic structure and stability of (001) surface of TiO2 in the anatase phase. In the framework of ab-initio atomistic thermodynamic, we argue that the anatase TiO2 prefers a defected oxygen layer termination in the (001) direction. The obtained electronic structures indicate that deep hydrogen doping in this stable termination creates a mid-gap state about 0.52 eV below the conduction band and hence decreases the band gap of the system. This phenomenon may explain the enhanced photocatalytic activity of the anatase TiO2 (001) surface after hydrogenation.
ICTPICTPpio@ictp.it

Europe/RomeAbstract:
The effect of hole doping on the Tight-Binding (TB) model of the Cu-O planes in the La2CuO4 constructed in previous works is investigated here. Firstly, it is pointed out that the model employed constitutes a generalization of the Hubbard one for the same system. Thus, the former predictions of the insulator gap, antiferromagnetic (AF) character and the existence of a paramagnetic-pseudogap (PPG) state at half-filling, become natural ones to be expected from this more general picture. The effect of hole doping on the antiferromagnetic-insulator state (AFI) and the paramagnetic-pseudogap one at half-filling, is investigated here at T = 0 K. The results predict the occurrence of a quantum phase transition (QPT) from the antiferromagnetic- insulator state at low doping to a paramagnetic-metallic state (PM) at higher hole densities. Therefore, a clear description of the hidden QPT laying beneath the “dome” in high critical temperature (HTc) superconducting materials is found. At low doping, the systems prefers the AFI state, and at the critical value of the doping density dc = 0.2, the energy of a metallic state starts becoming lower. The evolution with small doping values of the band spectrum of the AFI state, shows that the holes tend to become localized at the middle of the sides of the reduced Brillouin zone (BZ). Then, when passes through the critical value, the holes of the AFI state move to become situated at the corners of the same reduced BZ, showing in this way a structural change at the phase transition point. It suggests that the Kramers degeneration in combination with the spin-spatial entangled nature of the hole states, can lead to a new kind of pair interaction between two holes. The binding energy value is estimated as a function of the screening.
ICTPICTPpio@ictp.it

Europe/RomeThis is the continuation of the Applied Physics Seminars. You will be especially welcome if you are visiting the Centre, or another Trieste Institute, as Associate Members, TRIL Fellows, or if you are from Affiliated Institutes in the various areas of Applied Physics.
The summary of the seminar is available at:
http://www.ictp.it/~chelaf/ss319.htmlICTPICTPpio@ictp.it

Europe/RomeAbstract:
We give a topological description of cohomogeneity two Riemannian manifolds of negative curvature which are either locally symmetric or there is no singular orbit of positive
dimension.
As an application, we classify cohomogeneity k, k<4, Riemannian manifolds of constant negative curvature.
ICTPICTPpio@ictp.it

Europe/RomeWorldwide, women constitute a decided minority in the physics community.
There are four main arguments for increasing the number of women in physics:
(i) As with any intellectual activity, physics ought to be inclusive and be practised by a diverse body of scientists.
(ii) In an era when too few good students take up physics, it is especially foolish to be effectively excluding half the student population.
(iii) In the absence of role models, talented girls are less likely to take up physics.
(iv) When there are very few women in physics, these women often face a hostile or unsupportive work environment, that makes it difficult for them to thrive and do good work.
This is obviously a large and multi-faceted problem with complicated societal causes and implications.
We will not attempt to tackle all aspects of these in this short workshop. Our target group is working women physicists from all over the world, with a special focus on developing countries. What we would like to do for these women scientists is:
• Help them establish a worldwide network of women scientists who can provide support,
• advice, and role models.
• Help them build self-confidence (Many studies have shown that a lack of self-esteem • hampers women in their rise up the academic ladder).
• Help them gain the professional skills that they need to succeed in their careers.
The programme will feature inspiring talks by successful women physicists as well as talks on how to develop professional skills such as writing scientific papers and giving talks.
Participants will also give poster presentations on their research work, which will enable them to exchange ideas, network and build scientific contacts. ICTPICTPpio@ictp.it

Europe/RomeThis is the continuation of the Applied Physics Seminars. You will be especially welcome if you are visiting the Centre, or another Trieste Institute, as Associate Members, TRIL Fellows, or if you are from Affiliated Institutes in the various areas of Applied Physics.
The summary of the seminar is available at:
http://www.ictp.it/~chelaf/ss320.htmlICTPICTPpio@ictp.it

Europe/RomeThe Science Dissemination Unit (SDU) of the Abdus Salam International Centre for Theoretical Physics (ICTP) will organize a workshop on Science Dissemination and On-line Certification for All, to be held at the ICTP, Trieste, Italy from September 30 to October 2, 2013.
The workshop aims to guide the scientific community in developing countries into the potentialities of new, low-cost scientific pedagogical tools for the creation, and dissemination of on-line educational resources at a large-scale.
The workshop also aims to give a balanced mix of technical detail, general overview and societal impact. Suggested topics include: Massive on-line open courses (MOOCs); Infrastructure, design and technological issues with video capturing; Video course development and cultural issues in video learning systems; Asynchronous and synchronous web casting systems, Apps; Creative uses of video and role of rich-media in science; Particular attention will be paid towards innovation within a scientific environment.ICTPICTPpio@ictp.it

Europe/RomeINVITED LECTURERS: Roger Webb (University of Surrey, England), Chris Jeynes (University of Surrey, England), Nuno Barradas (Instituto Superior Técnico, Portugal).
TOPICS TO BE COVERED:
Introduction to accelerator based techniques.
Elemental and isotopic analysis and depth profiling.
Heavy ions: probing the entire periodic table.
Sensitivity and resolution.
Total IBA: synergistic treatment of data from multiple IBA techniques.
Learning and using state of the art codes to affect the IBA analyses.
Pitfalls in IBA data analysis.
Calculation of uncertainties in IBA.
Beyond Elemental Analysis; MeV-SIMS, High resolution PIXE.
Heavy Ion PIXE – the complement to MeV-SIMS.
TO ALL PARTICIPANTS: - Participants are encouraged to bring their laptop as the spectrum evaluation software will be installed onto them. - "Spectrum-Clinic": The Lecturers will provide help in the evaluation of complex spectra measured by the Participants. Please feel free to bring and share your scientific problems during the course. ICTPICTPpio@ictp.it

Europe/RomeThis is the continuation of the Applied Physics Seminars. You will be especially welcome if you are visiting the Centre, or another Trieste Institute, as Associate Members, TRIL Fellows, or if you are from Affiliated Institutes in the various areas of Applied Physics.
The summary of the seminar is available at:
http://www.ictp.it/~chelaf/ss323.htmlICTPICTPpio@ictp.it

Europe/RomeAbstract. The isotropy and homogeneity of the cosmic microwave background (CMB) favors "scalar driven" early Universe inflationary models. Non-scalar fields, and in particular gauge fields, are on the other hand commonplace in all high energy particle physics models proposed to be at work at the upper bound on energy scale of inflation set by the current CMB observations. In this review we consider the role and consequences, theoretical and observational, that gauge fields can have during inflationary era. Gauge fields may be turned on in the background during inflation, or may become relevant at the level of cosmic perturbations.
There have been two main class of models with gauge fields in the background, models which show violation of cosmic no-hair theorem and those which lead to isotropic FLRW cosmology, respecting the cosmic no-hair theorem. Models in which gauge fields are only turned on at the cosmic perturbation level, may source primordial magnetic fields. We also review specific observational features of these models on the CMB and/or the primordial cosmic magnetic fields. Our discussions will be mainly focused on the inflation period, with only a brief discussion on the post inflationary (p)reheating era.ICTPICTPpio@ictp.it

Europe/RomeThe Abdus Salam International Centre for Theoretical Physics (ICTP) in collaboration with the University Félix Houphouët-Boigny, Abidjan Cocody are organising the "Capacity Building Workshop on Modelling of Regional Climate and Air Quality for West Africa", to be held from 07 - 11 October 2013 in Abidjan, Côte d'Ivoire.
West Africa is one of the most important aerosols source in World due to the mixing of dust and combustion particles present into its atmosphere. These particles interact with regional climate and influence the regional air quality. So it appears important to reinforce the regional capacities about Regional climate studies and air quality monitoring.
The goals of this workshop are to facilitate cooperation initiative with ICTP and to develop network for ideas and expertise exchange.
Secretariat:
"Capacity Building Workshop on Modelling of Regional Climate and Air Quality for West Africa"
c/o SMR 2392 - ICTP
Strada Costiera 11
I-34151 Trieste, Italy
Telefax: +39-040-22407455
E-mail: smr2392@ictp.it
ICTP Home Page: http://www.ictp.it/Abidjan - Cote d'IvoireICTPpio@ictp.it

Europe/RomeThis period rich with experimental data releases is a great motivation for a focused workshop which brings together experimental and theoretical community, both in astro-particle and dark matter indirect searches, with a main motivation to form a "clean thought" on the topics, and an updated outlook on future directions.
Questions as: "where do we go from here?" will need to be addressed, covering basically the physics case and experimental ideas for the next generation in gamma - CR astroparticle studies, relevant for DM searches. ICTPICTPpio@ictp.it

Europe/RomeTo place tighter constraints on the physics of the early Universe, its expansion history and the nature of gravity, a better understanding of the nature of the bias between observable and dark matter will be needed.
The workshop will be an occasion to present and discuss the most recent developments in the understanding of this bias, along with insights from recent observations. ICTPICTPpio@ictp.it

Europe/RomeWater is one of the most ubiquitous substances in the universe. Despite long study from both experimental and theoretical approaches, phenomena associated with liquid water and its coupling to other systems continues to be a source of rather rich and interesting physics. In this talk, I will discuss how computational studies play an important role in probing both the structure and dynamics of water in different environments. I will motivate the discussion by briefly talking about water near the vicinity of proteins and the coupling between protein and water motions. I will then move onto some more recent work on trying to understand water as a hydrogen bond network and its subsequent role on processes like proton transfer in liquid water and anomalous water diffusion around ions like CsI and NaCl. I will also briefly touch on the role of nuclear quantum effects in altering the structural and electronic properties of water and its constituent ions.ICTPICTPpio@ictp.it

Europe/RomeAbstract. I will explain the spectator scenario and show its advantages compared to the curvaton scenario, under the latest Planck constraints. The spectator scenario generates a smaller non-Gaussianity, negligible isocurvature perturbations, and less tuning. It agrees well with the current Planck data in the visible sector inflation setup, as an example. It also explains the CMB dipole asymmetry with a brief fast roll phase. I will close the talk by proposing the CMB power multipoles, as an alternative approach independent of the CMB dipole asymmetry model.
ICTPICTPpio@ictp.it

Europe/RomeThis is the continuation of the Applied Physics Seminars. You will be especially welcome if you are visiting the Centre, or another Trieste Institute, as Associate Members, TRIL Fellows, or if you are from Affiliated Institutes in the various areas of Applied Physics.
The summary of the seminar is available at:
http://www.ictp.it/~chelaf/ss321.htmlICTPICTPpio@ictp.it

Europe/RomeWe begin with a pedagogical introduction to the Physics of the Mott Insulator to Superfluid transition (MI-SF)and its recent realization in cold-atomic system. Then we elaborate on such MI-SF transition in systems with two species of ultra-cold bosonic atoms in a two-dimensional square optical lattice with nearest- neighbor hopping amplitude t and a spin-orbit coupling k_SO. We chart out the phase diagram for the MI-SF transition using both a strong-coupling expansion and Gutzwiller mean-field theory. The momentum distribution near the MI-SF transition is shown to give precursor peaks. We analyze the critical theory of the transition revealing the presence of unconventional quantum critical points at t/k_SO=0, which are accompanied by the emergence of an additional gapless mode in the critical region. The Gutzwiller mean-field theory shows the existence of a twisted superfluid phase. We study the distribution of phases and the magnitude of the SF order parameter as a function of t and k_SO. We also study the collective modes and the dynamics of the phases in the semi-classical approach.ICTPICTPpio@ictp.it

Europe/RomeThe workshop will continue the series of “Nuclear Data for Science and Technology” workshops initiated in 1999, and held at regular intervals since then. Since the late 20th century many new non-energy applications of nuclear techniques have been developed, accompanied by a growing need for new and improved nuclear data. New applications include: nuclear medicine, astrophysics, transmutation, materials analysis, thin layer activation techniques, accelerator-driven technologies, and measurements of nuclear quantities for basic science, all of which frequently require the use and understanding of charged-particle data. Ion Beam Analysis (IBA) is a powerful analytical technique that makes substantial use of nuclear data for a wide range of applications in materials science, art, archaeology, geology, surface and interface engineering as well as environmental studies. IBA exploits the interactions of rapid charged particles (from ~0.1 to a few MeV) with matter to determine the composition and structure of the surface regions of solids. Considerable effort has been devoted by the IAEA to improve the nuclear data required for this technique, resulting in the creation of the IBANDL database. The efficient application of these IBA techniques requires appropriately trained and dedicated physicists.
Topics to be covered: * nuclear data and on-line retrieval systems * fundamentals of energetic particle interaction with matter, atoms and nuclei * overview of IBA techniques (RBS, ERDA, EBS, NRA, PIGE) * nuclear data for IBA – IBANDL data library * nuclear data for Particle Induced Gamma ray Emission (PIGE) * applications of IBA and PIGE in particular
PARTICIPATION Scientists and students from all countries which are members of the United Nations, UNESCO or IAEA may attend the School. As it will be conducted in English, participants should have an adequate working knowledge of that language. Although the main purpose of the Centre is to help research workers from developing countries, through a programme of training activities within a framework of international cooperation, a limited number of students and post-doctoral scientists from developed countries are also welcome to attend. As a rule, travel and subsistence expenses of the participants should be borne by the home institution. Every effort should be made by candidates to secure support for their fare (or at least half-fare). However, limited funds are available for some participants who are nationals of, and working in, a developing country. Such support is available only for those who attend the entire activity.
There is no registration fee. ICTPICTPpio@ictp.it

Europe/RomeThere has been strong interest in recent years in applying the notions of circulation regimes, weather regimes and weather types to a variety of time scales and applications, from weather forecasts to intra-seasonal anomalies to climate impacts.
The spatial scales covered by diverse classification schemes range from regional to hemispheric. There has also been an interest in applying weather types to such diverse subjects as pollution concentrations and human mortality. The purpose of the workshop will be to bring together researchers who apply classification techniques to describe and verify weather forecasts, climate anomalies over a range of time scales, and applications of human dimension.
The variety of mathematical and statistical techniques used will be presented, leading to cross-fertilization of techniques and methods.
Topics of interest will include:
• What are the common techniques used to describe large-scale circulation regimes and local weather types (e.g.cluster analysis, hidden Markov method, pdf analysis), and how are they related to each other?
• How are regimes used to characterize and verify forecasts from operational forecasting centers?
• How much is really understood about measuring the significance of deviations from Gaussian behavior, and the robustness of clustering / weather typing?
• Will climate change lead to an alteration of the frequency of occurrence of well-define regimes, or the modification of the whole regime structure?
• How can we describe coherent propagating structures, such as the Madden-Julian Oscillation (MJO) and the Monsoon intra-seasonal oscillation (ISO) in terms of regimes? “Hands-on” training sessions will be held in weather typing and circulation regime analysis, using data sets such as ERA-40 or NCEP reanalyses, and simple classification techniques which can be applied to their home regions for problems of local interest.
ICTPICTPpio@ictp.it

Europe/RomeThe school comprises different modules, containing lectures and practical applications.
Starting with an introduction to climate modelling and different downscaling approaches, downscaling of weather extremes will be studied in detail with a comparison of statistical and dynamical approaches, followed by an introduction to methods for validating the representation of extreme events and assessing their uncertainties. ICTPICTPpio@ictp.it

Europe/RomeBy a symbolic extension of a topological dynamical system (X,T) we mean an extension of (X,T) which is a subshift over a finite alphabet. The existence and the entropy of these extensions are related to the convergence of the metric entropy of (X,T) computed at finer and finer scales. T. Downarowicz and S. Newhouse have conjectured that any C^r with r>1 map on a compact manifold admits symbolic extensions. In this talk we will discuss the case of surface maps.
ICTPICTPpio@ictp.it

Europe/RomeWe consider a quantum quench of the trap frequency in a system of bosons interacting through an inverse-square potential and confined in a harmonic trap (the harmonic Calogero model). We determine exactly the initial state in terms of the post-quench eigenstates and derive the time evolution of simple physical observables. Since this model possesses an infinite set of integrals of motion (IoM) that allow its exact solution, a generalised Gibbs ensemble (GGE), i.e. a statistical ensemble that takes into account the conservation of all IoM, can be proposed in order to describe the values of local physical observables long after the quench. Even though, due to the presence of the trap, physical observables do not exhibit equilibration but periodic evolution, such a GGE may still describe correctly their time averaged values. We check this analytically for the local boson density and find that the GGE conjecture is indeed valid, in the thermodynamic limit.SISSA, Santorio Building, Room 5 (Ground floor)ICTPpio@ictp.it

starting October 23 at lunch time and ending October 25 at lunch time.

Europe/RomeGiven a finite subgroup G in SL(2, C), the classical McKay correspondence relates the representation theory of G and the cohomology of the minimal resolution of the singular surface C^2/G. I will discuss a modern formulation of this correspondence, with introductions to the relevant
notions, and present the problem I am currently working on. The talk will be aimed at a general maths audience including Ph.D. students.ICTPICTPpio@ictp.it

Europe/RomeIn modeling electronic and optical properties of molecular materials it is of fundamental interest to estimate charge and exciton transfer couplings between molecular sites. A short review of some quantum chemical based approaches to evaluate such couplings will be presented, focusing especially on triplet exciton transfer as example.ICTPICTPpio@ictp.it

Europe/RomeSystems in cavity or circuit QED (Quantum Electrodynamics) are extensively studied in the context of quantum information and quantum computing. In addition, studying the non-equilibrium dynamics of photons in these open quantum systems is a challenging theoretical question. Studying “versatile lattice versions of these systems” open new doors to quantum simulation, similar to ultra-cold atoms in optical lattices. In this Talk, we review our recent theoretical progress regarding (i) the development of methods to address the dynamics of driven and dissipative light-matter systems beyond the weak-coupling limit and (ii) the realization of topological phases of light in superconducting QED-circuit arrays through synthetic gauge fields. Effects of disorder will be studied. We also comment on the current experimental status in circuit QED systems.ICTPICTPpio@ictp.it

Activity

Europe/RomeDue to experiments in cold-atomic gases, the study of quantum quenches has become an active topic of research. While many rigorous results exist for exactly solvable "free" theories, not much is known about the effect of non-linearities, especially at long times and for systems in the thermodynamic limit, where numerical studies are challenging. In this talk, in order to highlight the main questions, I will first present results for a quench in an exactly solvable theory, namely the Luttinger model. I will then present results for the effect of various non-linearities such as a commensurate periodic potential and a local back-scattering potential.
I will show that the dynamics following a quench can be quite complex by being characterized by three regimes. One is a short time perturbatively accessible regime which depends on microscopic parameters, the second is an intermediate time prethermalized regime where inelastic effects are weak and correlation functions show universal scaling behavior which is quantified by a nonequilibrium generalization of the Callan-Symanzik equations. The third is a long time regime where inelastic effects become important. For the case of the commensurate periodic potential, I will show that these inelastic effects cause the system to eventually thermalize, where the thermalization time depends in a non-monotonic way on the quench amplitude.
SISSA, Santorio Building, Room 129 (1st Floor)ICTPpio@ictp.it

Seminar

28 Oct 2013

@ SISSA, Santorio Building, Room 129 (1st Floor)

Condensed Matter and Statistical Physics

Europe/RomeAbstract. We construct topological defects generating non-abelian T-duality for isometry groups acting without isotropy. We find that these defects are given by line bundles on the correspondence space with curvature which can be considered as a non-abelian generalization of the curvature of the Poincar\`{e} bundle. We show that the defect equations of motion encode the non-abelian T-duality transformation. The Fourier-Mukai transform of the Ramond-Ramond fields generated by the gauge invariant flux of these defects is studied. We show that it provides elegant and compact way of computation of the transformation of the Ramond-Ramond fields under the non-abelian T-duality.
ICTPICTPpio@ictp.it

Europe/RomeAmong the wealth of possible non-equilibrium many-body configurations most interesting candidates are those which show universal behavior. New, non-thermal fixed points are proposed, leading beyond standard equilibrium critical points. A selection of phenomena in ultracold Bose gases, characterized by specific power-laws in space and time, and universal time evolution will be presented. These are, for generic cases, related to the presence and turbulent dynamics of (quasi-)topological defects in the Bose field, which are manifestly far from equilibrium. Examples how to reach these critical points which will be discussed include interaction quenches and rapid evaporative cooling. Our results confirm non-perturbative quantum field theoretical predictions and establish a new link between kinetic wave turbulence and topological excitations of superfluids. They open a path to explore a new class of universal far-from-equilibrium dynamics well accessible in ultracold gas experiments. These phenomena are of importance far beyond the realm of cold gases and allow a view on new classifications of universal far-from-equilibrium physics.ICTPICTPpio@ictp.it

Europe/RomeA large variety of complex systems, from the brain to the weather networks and complex infrastructures, are formed by several networks that coexist, interact and coevolve forming a “network of networks”. Modeling such multilayer structures and characterizing the rich interplay between their structure and their dynamical behavior is crucial in order to understand and predict complex phenomena. In this talk I will present recent works on statistical mechanics of multiplex networks. Multiplex networks are formed by N nodes linked in different layers by different networks. I will present models that generate multiplexes with different types of correlations between the layers, and characterize new percolation phenomena on multiplex networks, showing first order phase transitions, bistability or a complex phase diagram with tricriticals points and higher order critical points.ICTPICTPpio@ictp.it

Europe/RomeThe study of the dynamics of thermally isolated many-body systems offers a unique opportunity to address the role of universality in nonequilibrium quantum phenomena. In this talk I will discuss recent results concerning the statistics of the work and of other observables in spin chains and bosonic systems out of equilibrium. I will show that the statistics of the work at low energies for spin chains (or bosonic systems) subject to a generic local or global variation of the transverse field is independent on the detail of the protocol, an example of universal behaviour both in time and space. I will similarly show that the statistics of excitations can be used to discuss universality and detect efficiently dynamical phase transitions.ICTPICTPpio@ictp.it

Europe/RomeIntroduction to Nakajima quiver varieties I:
Given a for a given quiver without loops, we will aim to state that
certain homology groups of Nakajima quiver varieties admit an action of
the underlying Kac-Moody algebra. We will define or sketch the terms there
in and do the examples corresponding to the Dynkin diagrams of type A1 and
A2.ICTPICTPpio@ictp.it

Europe/RomeIn this talk, I will review the recent results we have obtained on the SU(N) Heisenberg model of quantum permutations, which describes the low-energy properties of a number of Mott insulating phases in condensed matter physics (spin-1 antiferromagnets with biquadratic interaction, symmetric spin-orbital model) and cold atoms (ultracold ferminionic alkaline rare-earths in optical lattices). In 1D, where Quantum Monte Carlo simulations can be performed, we have calculated the correlations as a function of the entropy per site, with the conclusion that the entropy below which characteristic features show up increases with N and reaches experimentally accessible values already for N=4.
In 2D, using a variety of analytical and numerical approaches, in particular flavour-wave theory and a tensor-network algorithm, we have shown that the nature of the ground state depends crucially on the value of N and on the topology of the lattice, including long-range color order for SU(3) on the triangular and square lattices, spontaneous dimerization for SU(4) on the square lattice, and an algebraic quantum liquid for SU(4) on the honeycomb lattice. Experimental implications for condensed matter systems and cold atoms will be briefly discussed.
ICTPICTPpio@ictp.it

Europe/RomeAbstract. The discovery of the accelerating expansion of the Universe is motivating an impressive amount of theoretical and observational activity. After briefly reviewing the problems and challenges of "Dark Energy", I will focus on recent and ongoing works where a unifying description of dark energy and modified gravity is proposed, that is inspired by the Effective Field Theory (EFT) of Inflation formalism. By extending such a framework to late time cosmology one can write the most general action for cosmological perturbations in the presence of an additional scalar degree of freedom. I will focus on a few operators that are quadratic in the perturbations and which appear in non-minimally coupled scalar-tensor gravity and "Galileon" theories and describe the mixing between gravity and the scalar degree of freedom that such operators produce. I will also discuss the present observational constraints and forecasts for future experiments such as EUCLID. ICTPICTPpio@ictp.it

Europe/RomeThis is the continuation of the Applied Physics Seminars. You will be especially welcome if you are visiting the Centre, or another Trieste Institute, as Associate Members, TRIL Fellows, or if you are from Affiliated Institutes in the various areas of Applied Physics.
The summary of the seminar is available at:
http://www.ictp.it/~chelaf/ss323.htmlICTPICTPpio@ictp.it

Activity

Europe/RomeI will discuss recent developments for the Anderson model on the Bethe lattice. In particular I will present evidence in favour of a non-ergodic, extended phase before the Anderson transition sets in.ICTPICTPpio@ictp.it

Europe/RomeThis is the continuation of the Applied Physics Seminars. You will be especially welcome if you are visiting the Centre, or another Trieste Institute, as Associate Members, TRIL Fellows, or if you are from Affiliated Institutes in the various areas of Applied Physics.
The summary of the seminar is available at:
http://www.ictp.it/~chelaf/ss322.htmlICTPICTPpio@ictp.it